Acoustic output apparatus

ABSTRACT

The present disclosure provides an acoustic output apparatus including one or more status sensors, at least one low-frequency acoustic driver, at least one high-frequency acoustic driver, at least two first sound guiding holes, and at least two second sound guiding holes. The status sensors may detect status information of a user. The low-frequency acoustic driver may generate at least one first sound, a frequency of which is within a first frequency range. The high-frequency acoustic driver may generate at least one second sound, a frequency of which is within a second frequency range including at least one frequency exceeding the first frequency range. The first and second sound guiding holes may output the first and second spatial sound, respectively. The first and second sound may be generated based on the status information, and may simulate a target sound coming from at least one virtual direction with respect to the user.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/172,012, filed on Feb. 9, 2021, which is a Continuation ofInternational Application No. PCT/CN2020/087526, filed on Apr. 28, 2020,which claims priority to Chinese Patent Application No. 201910888067.6,filed on Sep. 19, 2019, Chinese Patent Application No. 201910888762.2,filed on Sep. 19, 2019, and Chinese Patent Application No.201910364346.2, filed on Apr. 30, 2019, the contents of each of whichare hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure generally relates to acoustic output apparatus,and more particularly, relates to acoustic output apparatus that canprovide a spatial sound related to a virtual reality (VR) scene or anaugmented reality (AR) scene to a user.

BACKGROUND

With the development of technology, smart VR/AR devices (e.g., smartglasses) are more and more popular. In some cases, open acoustic outputapparatuses may be provided on the smart VR/AR devices to output soundsrelated to a VR/AR scene. An open acoustic output apparatus is aportable audio output apparatus that can spread a sound within aspecific range, which allows a user to obtain sound information in thesurrounding environment while listening to the sound outputted by theacoustic output apparatus. An open structure of the open acoustic outputapparatus may lead to sound leakage that causes the sound outputted bythe open binaural acoustic output apparatus to be possibly heard byother people around a user wearing the open acoustic output apparatus.Therefore, it is desirable to provide novel acoustic output devices thatcan reduce sound leakage and enhance an audio experience for the user.

SUMMARY

According to an aspect of the present disclosure, an acoustic outputapparatus is provided. The acoustic output apparatus may include one ormore status sensors, at least one low-frequency acoustic driver, atleast one high-frequency acoustic driver, at least two first soundguiding holes, and at least two second sound guiding holes. The one ormore status sensors may be configured to detect status information of auser. The at least one low-frequency acoustic driver may be configuredto generate at least one first sound, wherein a frequency of the atleast one first sound being within a first frequency range. The at leastone high-frequency acoustic driver may be configured to generate atleast one second sound. A frequency of the at least one second sound maybe within a second frequency range, wherein the second frequency rangeincludes at least one frequency that exceeds the first frequency range.The at least two first sound guiding holes may be acoustically coupledto the at least one low-frequency acoustic driver. The at least twofirst sound guiding holes may be configured to output the at least onefirst sound. The at least two second sound guiding holes may beacoustically coupled to the at least one high-frequency acoustic driver.The at least two second sound guiding holes may be configured to outputthe second spatial sound. The at least one first sound and the at leastone second sound may be generated based on the status information. Theat least one first sound and the at least one second sound may beconfigured to simulate at least one target sound coming from at leastone virtual direction with respect to the user.

In some embodiments, there may be a first distance between the at leasttwo first sound guiding holes and a second distance between the at leasttwo second sound guiding holes. The first distance may be greater thanthe second distance.

In some embodiments, the first distance may be with a range of 20 mm-40mm.

In some embodiments, the second distance may be within a range of 3 mm-7mm.

In some embodiments, the first distance may be greater than or equal totwo times of the second distance.

In some embodiments, the first frequency range may include at least onefrequency that is lower than 650 Hz, and the second frequency range mayinclude at least one frequency that is higher than 1000 Hz.

In some embodiments, the first frequency range may overlap with thesecond frequency range.

In some embodiments, the acoustic output apparatus may further includean electronic frequency division module. The electronic frequencydivision module may be configured to divide a sound signal into a firstsound signal corresponding to a sound of the first frequency range and asecond sound signal corresponding to a sound of the second frequencyrange. The first sound signal may be transmitted to the at least onelow-frequency acoustic driver and the second sound signal may betransmitted to the at least one high-frequency acoustic driver.

In some embodiments, the electronic frequency division module mayinclude at least one of a passive filter, an active filter, an analogfilter, or a digital filter.

In some embodiments, the at least one low-frequency acoustic driver mayinclude a first transducer, and the at least one high-frequency acousticdriver may include a second transducer. The first transducer and thesecond transducer may have different frequency response characteristics.

In some embodiments, the first transducer may include a low-frequencyspeaker, and the second transducer may include a high-frequency speaker.

In some embodiments, the at least two first sound guiding holes may becoupled to the at least one low-frequency acoustic driver via a firstacoustic route, and the at least two second sound guiding holes may becoupled to the at least one high-frequency acoustic driver via a secondacoustic route. The first acoustic route and the second acoustic routemay have different frequency selection characteristics.

In some embodiments, the first acoustic route may include an acousticimpedance material. The acoustic impedance of the acoustic impedancematerial may be within a range of 5 MKS Rayleigh to 500 MKS Rayleigh.

In some embodiments, the acoustic output apparatus may further include asupporting structure. The supporting structure may be configured tocarry the at least one low-frequency acoustic driver and the at leastone high-frequency acoustic driver, and enable the acoustic outputapparatus to be located off the user ear.

In some embodiments, a distance between each of the at least two firstsound guiding holes and an ear of the user may be greater than adistance between each of the at least two second sound guiding holes andthe ear of the user.

In some embodiments, the at least two first sound guiding holes and theat least two second sound guiding holes may be located on the supportingstructure.

In some embodiments, the at least one low-frequency acoustic driver maybe enclosed in a first housing, wherein the first housing forms a firstfront chamber of the at least one low-frequency acoustic driver and afirst rear chamber of the at least one low-frequency acoustic driver.

In some embodiments, the first front chamber may be acoustically coupledto one of the at least two first sound guiding holes, and the first rearchamber may be acoustically coupled to another one of the at least twofirst sound guiding holes.

In some embodiments, the at least one high-frequency acoustic driver maybe enclosed in a second housing, wherein the second housing forms asecond front chamber of the at least one high-frequency acoustic driverand a second rear chamber of the at least one high-frequency acousticdriver.

In some embodiments, the second front chamber may be acousticallycoupled to one of the at least two second sound guiding holes, and thesecond rear chamber may be acoustically coupled to another one of the atleast two second sound guiding holes.

In some embodiments, a phase of one of the at least one first soundoutputted from one of the at least two first sound guiding holes may beopposite to a phase of another one of the at least one first soundoutputted from another one of the at least two first sound guidingholes.

In some embodiments, a phase of one of the at least one second soundoutputted from one of the at least two second sound guiding holes may beopposite to a phase of another one of the at least one second soundoutputted from another one of the at least two second sound guidingholes.

In some embodiments, the at least two first sound guiding holes mayinclude a first set of first sound guiding holes located in a firstregion of the acoustic output apparatus and a second set of first soundguiding holes located in a second region of the acoustic outputapparatus. The first region of the acoustic output apparatus and thesecond region of the acoustic output apparatus may be located atopposite sides of the user. The at least two second sound guiding holesmay include a first set of second sound guiding holes located in a thirdregion of the acoustic output apparatus and a second set of second soundguiding holes located in a fourth region of the acoustic outputapparatus. The third region of the acoustic output apparatus and thefourth region of the acoustic output apparatus may be located atopposite sides of the user.

In some embodiments, the at least one target sound coming from at leastone virtual direction with respect to the user may be simulated based onat least one of: a first difference between the at least one first soundoutputted by the first set of first sound guiding holes and the at leastone first sound outputted by the second set of first sound guidingholes, or a second difference between the at least one second soundoutputted by the first set of second sound guiding holes and the atleast one second sound outputted by the second set of second soundguiding holes.

In some embodiments, the first difference or the second difference mayinclude at least one of a phase difference, an amplitude difference, ora frequency difference.

In some embodiments, the acoustic output apparatus may further include adisplay configured to present visual data to the user based on thestatus information of the user.

In some embodiments, the acoustic output apparatus may further include acamera configured to obtain image data from a scene around the user inreal time.

Additional features will be set forth in part in the description whichfollows, and in part will become apparent to those skilled in the artupon examination of the following and the accompanying drawings or maybe learned by production or operation of the examples. The features ofthe present disclosure may be realized and attained by practice or useof various aspects of the methodologies, instrumentalities, andcombinations outlined in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplaryembodiments. These exemplary embodiments are described in detail withreference to the drawings. The drawings are not to scale. Theseembodiments are non-limiting exemplary embodiments, in which likereference numerals represent similar structures throughout the severalviews of the drawings, and wherein:

FIG. 1 is a schematic diagram illustrating exemplary two point sourcesaccording to some embodiments of the present disclosure;

FIG. 2 is a schematic diagram illustrating a variation of sound leakageof two point sources and a single point source along with frequencyaccording to some embodiments of the present disclosure;

FIGS. 3A-3B are graphs illustrating a volume of the near-field sound anda volume of the far-field leakage as a function of a distance of twopoint sources according to some embodiments of the present disclosure;

FIG. 4 is a schematic diagram illustrating an exemplary acoustic outputapparatus according to some embodiments of the present disclosure;

FIGS. 5A-5B are schematic diagrams illustrating exemplary applicationscenarios of an acoustic driver according to some embodiments of thepresent disclosure;

FIGS. 6A-6B are schematic diagrams illustrating exemplary sound outputsaccording to some embodiments of the present disclosure;

FIGS. 7A-7B are schematic diagrams illustrating acoustic outputapparatuses according to some embodiments of the present disclosure;

FIGS. 8A-8C are schematic diagrams illustrating acoustic routesaccording to some embodiments of the present disclosure;

FIG. 9 is an exemplary graph illustrating sound leakage under acombination of two sets of two point sources according to someembodiments of the present disclosure;

FIG. 10 is a schematic diagram illustrating another exemplary acousticoutput apparatus according to some embodiments of the presentdisclosure;

FIG. 11 is a schematic diagram illustrating two point sources andlistening positions according to some embodiments of the presentdisclosure.

FIG. 12 is a graph illustrating a variation of a volume of the soundheard by the user of two point sources with different distances as afunction of frequency according to some embodiments of the presentdisclosure;

FIG. 13 is a graph illustrating a variation of a normalized parameter oftwo point sources in a far-field along with frequency according to someembodiments of the present disclosure;

FIG. 14 is a distribution diagram illustrating an exemplary baffleprovided between two point sources according to some embodiments of thepresent disclosure;

FIG. 15 is a graph illustrating a variation of a volume of sound heardby the user as a function of frequency when an auricle is locatedbetween two point sources according to some embodiments of the presentdisclosure;

FIG. 16 is a graph illustrating a variation of a volume of the leakedsound as a function of frequency when an auricle is located between twopoint sources according to some embodiments of the present disclosure;

FIG. 17 is a graph illustrating a variation of a normalized parameter asa function of frequency when two point sources of an acoustic outputapparatus are distributed on both sides of an auricle according to someembodiments of the present disclosure;

FIG. 18 is a graph illustrating a variation of a volume of sound heardby the user and a volume of the leaked sound as a function of frequencywith and without a baffle between two point sources according to someembodiments of the present disclosure;

FIG. 19 is a graph illustrating a variation of a volume of sound heardby the user and a volume of the leaked sound as a function of thedistance between two point sources at a frequency of 300 Hz and with orwithout a baffle according to some embodiments of the presentdisclosure;

FIG. 20 is a graph illustrating a variation of a volume of sound heardby the user and a volume of the leaked sound as a function of thedistance between two point sources at a frequency of 1000 Hz and with orwithout a baffle according to some embodiments of the presentdisclosure;

FIG. 21 is a graph illustrating a variation of a volume of sound heardby the user and a volume of the leaked sound as a function of distanceat a frequency of 5000 Hz and with or without a baffle between the twopoint sources according to some embodiments of the present disclosure;

FIGS. 22-24 are graphs illustrating a variation of a volume of soundheard by the user as a function of frequency when a distance d of twopoint sources is 1 cm, 2 cm, 3 cm, respectively, according to someembodiments of the present disclosure;

FIG. 25 is a graph illustrating a variation of a normalized parameter asa function of frequency when a distance d of two point sources is 1 cmaccording to some embodiments of the present disclosure;

FIG. 26 is a graph illustrating a variation of a normalized parameter asa function of frequency when a distance d of two point sources is 2 cmaccording to some embodiments of the present disclosure;

FIG. 27 is a graph illustrating a variation of a normalized parameter asa function of frequency when a distance d of two point sources is 4 cmaccording to some embodiments of the present disclosure;

FIG. 28 is a graph illustrating exemplary distributions of differentlistening positions according to some embodiments of the presentdisclosure;

FIG. 29 is a graph illustrating a volume of sound heard by the user froma two point sources without baffle at different listening positions in anear-field as a function of frequency according to some embodiments ofthe present disclosure;

FIG. 30 is a graph illustrating a normalized parameter of two pointsources without baffle at different listening positions in a near-fieldaccording to some embodiments of the present disclosure;

FIG. 31 is a graph illustrating a volume of sound heard by the user fromtwo point sources with a baffle at different listening positions in anear-field as a function of frequency according to some embodiments ofthe present disclosure;

FIG. 32 is a graph illustrating a normalized parameter of two pointsources with a baffle at different listening positions in a near-fieldaccording to some embodiments of the present disclosure;

FIG. 33 is a schematic diagram illustrating two point sources and abaffle according to some embodiments of the present disclosure;

FIG. 34 is a graph illustrating a variation of a volume of thenear-field sound as a function of frequency when a baffle is atdifferent positions according to some embodiments of the presentdisclosure;

FIG. 35 is a graph illustrating a variation of a volume of the far-fieldleakage as a function of frequency when a baffle is at differentpositions according to some embodiments of the present disclosure;

FIG. 36 is a graph illustrating a variation of a normalization parameteras a function of frequency when a baffle is at different positionsaccording to some embodiments of the present disclosure;

FIG. 37 is a schematic diagram illustrating another exemplary acousticoutput apparatus according to some embodiments of the presentdisclosure;

FIG. 38 is a schematic diagram illustrating an exemplary acoustic outputapparatus customized for augmented reality according to some embodimentsof the present disclosure;

FIGS. 39A and 39B are schematic diagrams illustrating exemplary noisereduction systems according to some embodiments of the presentdisclosure;

FIGS. 40A and 40B illustrate exemplary frequency responses of a thirdmicrophone and exemplary frequency responses of a fourth microphoneaccording to some embodiments of the present disclosure;

FIG. 41 is a schematic diagram illustrating an exemplary user-interfaceof an acoustic output apparatus according to some embodiments of thepresent disclosure;

FIG. 42 is a schematic diagram illustrating an exemplary phase-modulatedsignal according to some embodiments of the present disclosure;

FIGS. 43A and 43B are schematic diagrams of exemplary smart glassesaccording to some embodiments of the present disclosure;

FIGS. 44A and 44B are schematic diagrams of exemplary legs of the smartglasses according to some embodiments of the present disclosure;

FIGS. 45A and 45B are schematic diagrams of another exemplary smartglasses according to some embodiments of the present disclosure;

FIG. 46A is a schematic diagram of an exemplary leg of the smart glassesaccording to some embodiments of the present application;

FIG. 46B is a schematic diagram of the other exemplary smart glassesaccording to some embodiments of the present application;

FIG. 47 is a schematic diagram of another exemplary smart glassesaccording to some embodiments of the present disclosure;

FIG. 48 is a schematic diagram of an exemplary acoustic output apparatusaccording to some embodiments of the present disclosure;

FIG. 49 is a block diagram illustrating an exemplary processor forsimulating a target sound coming from a sound source according to someembodiments of the present disclosure; and

FIG. 50 is a flowchart of an exemplary process for simulating a targetsound coming from the sound source according to some embodiments of thepresent disclosure.

DETAILED DESCRIPTION

In order to illustrate the technical solutions related to theembodiments of the present disclosure, a brief introduction of thedrawings referred to in the description of the embodiments is providedbelow. Drawings described below are only some examples or embodiments ofthe present disclosure. Those having ordinary skills in the art, withoutfurther creative efforts, may apply the present disclosure to othersimilar scenarios according to these drawings. Unless stated otherwiseor obvious from the context, the same reference numeral in the drawingsrefers to the same structure and operation.

As used in the disclosure and the appended claims, the singular forms“a,” “an,” and “the” include plural referents unless the content clearlydictates otherwise. It will be further understood that the terms“comprises,” “comprising,” “includes,” and/or “including” when used inthe disclosure, specify the presence of stated steps and elements, butdo not preclude the presence or addition of one or more other steps andelements.

Some modules of the system may be referred to in various ways accordingto some embodiments of the present disclosure, however, any number ofdifferent modules may be used and operated in a client terminal and/or aserver. These modules are intended to be illustrative, not intended tolimit the scope of the present disclosure. Different modules may be usedin different aspects of the system and method.

According to some embodiments of the present disclosure, flow charts areused to illustrate the operations performed by the system. It is to beexpressly understood, the operations above or below may or may not beimplemented in order. Conversely, the operations may be performed ininverted order, or simultaneously. Besides, one or more other operationsmay be added to the flowcharts, or one or more operations may be omittedfrom the flowchart.

Technical solutions of the embodiments of the present disclosure aredescribed with reference to the drawings. It is obvious that thedescribed embodiments are not exhaustive and are not limiting. Otherembodiments obtained, based on the embodiments outlined in the presentdisclosure, by those with ordinary skill in the art without any creativeworks are within the scope of the present disclosure.

An aspect of the present disclosure relates to an acoustic outputapparatus. The acoustic output apparatus may include one or moresensors, a controller, a target sound generation module, at least onelow-frequency acoustic driver, at least one high-frequency acousticdriver, at least two first sound guiding holes, and at least two secondsound guiding holes. The one or more sensors may include one or morestatus sensors configured to detect status information of a user. Thecontroller may be configured to generate a first sound signalcorresponding to a first frequency range and a second sound signalcorresponding to a second frequency range. The second frequency rangemay include frequencies higher than the first frequency range. Thetarget sound generation module may be configured to generate at leasttwo sound signals for simulating a target sound. The target sound may bea spatial sound that allows the user to identify the positioninformation of the sound source in a VR/AR scene. The at least onelow-frequency acoustic driver may be configured to generate a firstsound corresponding to the first frequency range. The at least onehigh-frequency acoustic driver may be configured to generate a secondsound corresponding to the second frequency range. The at least twofirst sound guiding holes may be acoustically coupled to the at leastone low-frequency acoustic driver and configured to output the firstsound. The at least two second sound guiding holes may be acousticallycoupled to the at least one high-frequency acoustic driver andconfigured to output the second sound. In some embodiments, the at leastone first sound and the at least one second sound may be configured tosimulate at least one target sound coming from at least one virtualdirection with respect to the user. The user may be able to identify adirection or a position of a sound source of the target sound. Thus, anaudio experience of the user ma be improved. For example, the at leasttwo first sound guiding holes may include a first set of sound guidingholes which are located at one side of a user (e.g., the left side closeto the left ear) and a second set of sound guiding holes which arelocated at another side of the user (e.g., the right side close to theright ear). The different sets of sound guiding holes may output soundswith different phases, different amplitudes, and/or differentfrequencies to simulate the at least one target sound.

According to another aspect of the present disclosure, the acousticoutput device may further include a noise reduction device configured toreduce the noise of sound detected by an audio sensor of the acousticoutput device. The noise reduction device can generate a plurality ofsub-band noise correction signal in response to the sub-band noisesignals. As a result, noise in the sound detected by the audio sensormay be effectively reduced or eliminated. The user may interact with theacoustic output device by, for example, speaking. Therefore, the userexperience for using the acoustic output device may be enhanced.

An acoustic output apparatus in the present disclosure may refer to adevice having a sound output function. In practical applications, theacoustic output apparatus may include different product forms such asbracelets, glasses, helmets, watches, clothing, or backpacks. Forillustration purposes, a glass with a sound output function may beprovided as an example. Exemplary glasses may include myopia glasses,sports glasses, hyperopia glasses, reading glasses, astigmatism lenses,wind/sand-proof glasses, sunglasses, ultraviolet-proof glasses, weldingmirrors, infrared-proof mirrors, smart glasses, or the like, or anycombination thereof. Exemplary smart glasses may include virtual reality(VR) glasses, augmented reality (AR) glasses, mixed reality (MR)glasses, mediated reality glasses, or the like, or any combinationthereof.

Taking the smart glasses as an example, the sound output function of theacoustic output apparatus is described hereinafter. The smart glassesmay include a microphone array. The microphone array may include aplurality of microphones. Each of the microphones may have a specificfrequency response to the sound. Each of the microphones may beconfigured to detect sound and generate a sub-band sound signal inresponse to the detected sound. For example, the microphone with ahigher frequency response may be more sensitive to high-frequency sound,and the microphone with a lower frequency response may be more sensitiveto low-frequency sound. The microphones with different frequencyresponses may improve the ability of the smart glasses to detect thesound and make a frequency response curve of the smart glasses flat,thereby improving a sound pickup effect of the smart glasses. In someembodiments, the smart glasses may further include a noise reductiondevice and a combination device. The noise reduction device may generatea plurality of noise correction signals according to the sub-band voicesignals. Each of the noise correction signals may be generated accordingto one of the sub-band voice signals. The microphone array may add anoise correction signal to the corresponding sub-band voice signal togenerate a sub-band correction signal. The combination device maycombine a plurality of sub-band correction signals generated by themicrophone array to generate a target sound signal.

In some embodiments, when the user wears the smart glasses, the smartglasses may be located on at least one side of the user's head, and beclose to but not blocking the user's ear. The smart glasses may be wornon the user's head (for example, non-in-ear open earphones worn withglasses, headbands, or other structural means) or on other parts of theuser's body, such as the user's neck/shoulder.

In some embodiments, the smart glasses may include at least two groupsof acoustic drivers, which may include at least one group ofhigh-frequency acoustic drivers and one group of low-frequency acousticdrivers. Each group of acoustic drivers may be used to generate a soundwith a certain frequency range, and the sound may be propagated outwardthrough at least two sound guiding holes that are acoustically coupledto it. By dividing (for example, decomposing into high and low-frequencysignals) the sound signal and setting different sound guiding holepitches for the frequency-divided signals in different frequency bands(for example, the distance between two sound guiding holes correspondingto the low-frequency acoustic driver may be set greater than thedistance between at least two sound guiding holes corresponding to thehigh-frequency acoustic driver), the leakage reduction capability of theopen binaural headphones may be improved.

In some embodiments, a baffle structure may be provided on the smartglasses, so that the at least two sound guiding holes may be distributedon both sides of the baffle, respectively. In some embodiments, the atleast two sound guiding holes may be distributed on both sides of theuser's auricle. At this time, the auricle may serve as a baffle, and theat least two sound guiding holes may be separated, so that thepropagation routes of the sound emitted from the at least two soundguiding holes to the user's ear canal may be different. By setting thebaffle, the propagation route of the sound from different sound guidingholes to the user's ear canal may be different, and the leakagereduction capability of the open binaural headphones may be improved.

FIG. 1 is a schematic diagram illustrating exemplary two-point soundsources according to some embodiments of the present disclosure. Inorder to further explain the effect of the setting of the sound guidinghole on the acoustic output apparatus on the sound output effect of theacoustic output apparatus, and considering that the sound may beregarded as propagating outwards from the sound guiding hole, thepresent disclosure may describe a sound guiding hole on an acousticoutput apparatus as a sound source for externally outputting sound.

Just for the convenience of description and for illustration, when thesize of the sound guiding hole on the acoustic output apparatus issmall, each sound guiding hole may be approximately regarded as a pointsource (or referred to as a point sound source or a sound source). Insome embodiments, any sound guiding hole provided on the acoustic outputapparatus for outputting sound may be approximated as a single-pointsound source on the acoustic output apparatus. The sound field pressurep generated by a single-point sound source may satisfy Equation (1):

$\begin{matrix}{{p = {\frac{j\omega\rho_{0}}{4\pi r}Q_{0}\exp j\left( {{\omega t} - {kr}} \right)}},} & (1)\end{matrix}$where ω is the angular frequency, ρ₀ is the air density, r is thedistance between a target point and the sound source, Q₀ is the volumevelocity of the sound source, and k is the wave number. It may be seenthat the magnitude of the sound field pressure of sound field of thepoint sound source at the target point is inversely proportional to thedistance from the target point to the point sound source.

It should be noted that the sound guiding holes for outputting sound aspoint sources may only serve as an explanation of the principle andeffect of the present disclosure, and may not limit the shapes and sizesof the sound guiding holes in practical applications. In someembodiments, if an area of a sound guiding hole is large enough, thesound guiding hole may also be equivalent to a planar acoustic source.In some embodiments, the point source may also be realized by otherstructures, such as a vibration surface and a sound radiation surface.For those skilled in the art, without creative activities, it may beknown that sounds produced by structures such as a sound guiding hole, avibration surface, and an acoustic radiation surface may be similar to apoint source at the spatial scale discussed in the present disclosureand may have similar sound propagation characteristics and the similarmathematical description method. Further, for those skilled in the art,without creative activities, it may be known that the acoustic effectachieved by “an acoustic driver may output sound from at least two firstsound guiding holes” described in the present disclosure may alsoachieve the same effect by other acoustic structures, for example, “atleast two acoustic drivers each may output sound from at least oneacoustic radiation surface.” According to actual situations, otheracoustic structures may be selected for adjustment and combination, andthe same acoustic output effect may also be achieved. The principle ofradiating sound outward with structures such as surface sound sourcesmay be similar to that of point sources, and may not be repeated here.

As mentioned above, at least two sound guiding holes corresponding tothe same acoustic driver may be set on the acoustic output apparatusprovided in the specification. In this case, two point sources may beformed, which may reduce sound transmitted to the surroundingenvironment. For convenience, sound output from the acoustic outputapparatus to the surrounding environment may be referred to as afar-field leakage since it can be heard by others in the environment.The sound output from the acoustic output apparatus to the ears of theuser wearing the acoustic output apparatus may be referred to as anear-field sound since a distance between the acoustic output apparatusand the user is relatively short. In some embodiments, the sound outputfrom two sound guiding holes (i.e., two point sources) may have acertain phase difference. When the distance between the two pointsources and the phase difference of the two point sources meet a certaincondition, the acoustic output apparatus may output different soundeffects in the near-field (for example, the position of the user's ear)and the far-field. For example, if the phases of the point sourcescorresponding to the two sound guiding holes are opposite, that is, anabsolute value of the phase difference between the two point sources is180 degrees, the far-field leakage may be reduced according to theprinciple of reversed phase destruction. More details regardingenhancement of the acoustic output apparatus by adjusting the amplitudeand/or phase of each point source may be found in InternationalApplication No. PCT/CN2019/130884, filed on Dec. 31, 2019, the entirecontent of which may be hereby incorporated by reference.

As shown in FIG. 1 , a sound field pressure p generated by two-pointsound sources may satisfy Equation (2):

$\begin{matrix}{{p = {{\frac{A_{1}}{r_{1}}\exp j\left( {{\omega t} - {kr_{1}} + \varphi_{1}} \right)} + {\frac{A_{2}}{r_{2}}\exp j\left( {{\omega t} - {kr_{2}} + \varphi_{2}} \right)}}},} & (2)\end{matrix}$where A₁ and A₂ denote intensities of the two-point sound sources, andφ₁ and φ₂ denote phases of the two-point sound sources, respectively, ddenotes a distance between the two-point sound sources, and r₁ and r₂may satisfy Equation (3):

$\begin{matrix}\left\{ {\begin{matrix}{r_{1} = \sqrt{r^{2} + \left( \frac{d}{2} \right)^{2} - {2*r*\frac{d}{2}*\cos\theta}}} \\{r_{2} = \sqrt{r^{2} + \left( \frac{d}{2} \right)^{2} + {2*r*\frac{d}{2}*\cos\theta}}}\end{matrix},} \right. & \left. 3 \right)\end{matrix}$where r denotes a distance between a target point and the center of thetwo-point sound sources in the space, and θ indicates an angle between aline connecting the target point and the center of the two-point soundsources and the line on which the two point sound source is located.

It may be known from Equation (3) that a magnitude of the sound pressurep at the target point in the sound field may relate to the intensity ofeach point sound source, the distance d, the phase of each point source,and the distance r.

Two point sources with different output effects may be achieved bydifferent settings of sound guiding holes, such that the volume of thenear-field heard may be improved, and the far-field leakage may bereduced. For example, an acoustic driver may include a vibrationdiaphragm. When the vibration diaphragm vibrates, sounds may be emittedfrom the front and rear sides of the vibration diaphragm, respectively.The front side of the vibration diaphragm in the acoustic outputapparatus may be provided with a front chamber for transmitting sound.The front chamber may be acoustically coupled with a sound guiding hole.The sound on the front side of the vibration diaphragm may betransmitted to the sound guiding hole through the front chamber andfurther transmitted outwards. The rear side of the vibration diaphragmin the acoustic output apparatus may be provided with a rear chamber fortransmitting sound. The rear chamber may be acoustically coupled withanother sound guiding hole. The sound on the rear side of the vibrationdiaphragm may be transmitted to the sound guiding hole through the rearchamber and propagate further outwards. It should be noted that, whenthe vibration diaphragm is vibrating, the front side and the rear sideof the vibration diaphragm may generate sounds with opposite phases. Insome embodiments, the structures of the front chamber and rear chambermay be specially set so that the sound output by the acoustic driver atdifferent sound guiding holes may meet a specific condition. Forexample, lengths of the front chamber and rear chamber may be speciallydesigned such that sound with a specific phase relationship (e.g.,opposite phases) may be output at the two sound guiding holes. As aresult, a problem that the acoustic output apparatus has a low volume inthe near-field and sound leakage in the far-field may be effectivelyresolved.

Under certain conditions, compared to the volume of a far-field leakageof a single point source, the volume of a far-field leakage of two pointsources may increase with the frequency. In other words, the leakagereduction capability of the two point sources in the far-field maydecrease with the frequency increases. For further description, a curveillustrating a relationship between a far-field leakage and a frequencymay be described in connection with FIG. 2 .

FIG. 2 is a schematic diagram illustrating a variation of sound leakageof two-point sound sources and a single-point sound source along withfrequency according to some embodiments of the present disclosure. Adistance between the two point sound sources in FIG. 2 may be fixed, andtwo point sound sources may have the substantially same amplitude andopposite phases. The dotted line may indicate a variation curve of avolume of a leaked sound of a single-point sound source at differentfrequencies. The solid line may indicate a variation curve of a volumeof a leaked sound of two-point sound sources at different frequencies.The abscissa of the diagram may represent the sound frequency (f), andthe unit may be Hertz (Hz). The ordinate of the diagram may use anormalization parameter a to evaluate the volume of a leaked sound. Theparameter a may be determined according to Equation (4):

$\begin{matrix}{{\alpha = \frac{{❘P_{far}❘}^{2}}{{❘P_{ear}❘}^{2}}},} & (4)\end{matrix}$where P_(far) represents the sound pressure of the acoustic outputapparatus in the far-field (i.e., the sound pressure of the far-fieldsound leakage). P_(ear) represents the sound pressure around the user'sears (i.e., the sound pressure of the near-field sound). The larger thevalue of α, the larger the far-field leakage relative to the near-fieldsound heard, which may indicate that a poorer capability of the acousticoutput apparatus for reducing the far-field leakage.

As shown in FIG. 2 , when the frequency is below 6000 Hz, the far-fieldleakage produced by the two-point sound sources may be less than thefar-field leakage produced by the single-point sound source, and mayincrease as the frequency increases; When the frequency is close to10000 Hz (for example, about 8000 Hz or above), the far-field leakageproduced by the two-point sound sources may be greater than thefar-field leakage produced by the single-point sound source. In someembodiments, a frequency corresponding to an intersection of thevariation curves of the two-point sound sources and the single-pointsound source may be determined as an upper limit frequency that thetwo-point sound sources are capable of reducing sound leakage.

For illustrative purposes, when the frequency is relatively small (forexample, in a range of 100 Hz-1000 Hz), the capability of reducing soundleakage of the two point sources may be strong (e.g., the value of a issmall, such as below −80 dB). In such a frequency band, an increase inthe volume of the sound heard by the user may be determined as anoptimization goal. When the frequency is larger (for example, in a rangeof 1000 Hz-8000 Hz), the capability of reducing sound leakage of the twopoint sources may be weak (e.g., above −80 dB). In such a frequencyband, a decrease of the sound leakage may be determined as theoptimization goal.

According to FIG. 2 , it may be possible to determine a frequencydivision point based on the variation tendency of the two point sources'capability of reducing sound leakage. Parameters of the two pointsources may be adjusted according to the frequency division point so asto reducing the sound leakage of the acoustic output apparatus. Forexample, the frequency corresponding to a of α specific value (forexample, −60 dB, −70 dB, −80 dB, −90 dB, etc.) may be used as thefrequency division point. Parameters of the two point sources may bedetermined to improve the near-field sound in a frequency band below thefrequency division point, and/or to reduce the far-field sound leakagein a frequency band above the frequency division point. In someembodiments, a high-frequency band with a high frequency (for example, asound output from a high-frequency acoustic driver) and a low-frequencyband with a low frequency (for example, a sound output from alow-frequency acoustic driver) may be determined based on the frequencydivision point. More details of the frequency division point may bedisclosed elsewhere in the present disclosure, for example, FIG. 8 andthe descriptions thereof.

In some embodiments, the method for measuring and determining the soundleakage may be adjusted according to the actual conditions. For example,a plurality of points on a spherical surface centered by s center pointof the two point sources with a radius of r (for example, 40centimeters) may be identified, and an average value of amplitudes ofthe sound pressure at the plurality of points may be determined as thevalue of the sound leakage. The distance between the near-fieldlistening position and the point sources may be far less than thedistance between the point sources and the spherical surface formeasuring the far-field leakage. Optionally, the ratio of the distancefrom the near-field listening position to the center of the two pointsources to the radius r may be less than 0.3, 0.2, 0.15, or 0.1. Asanother example, one or more points of the far-field may be taken as theposition for measuring the sound leakage, and the sound volume of theposition may be taken as the value of the sound leakage. As anotherexample, a center of the two point sources may be used as a center of acircle at the far-field, and sound pressure amplitudes of two or morepoints evenly distributed at the circle according to a certain spatialangle may be averaged as the value of the sound leakage. These measuringand calculating methods may be adjusted by those skilled in the artaccording to actual conditions, and may not be limited herein.

According to FIG. 2 , it may be concluded that in the high-frequencyband (a higher frequency band determined according to the frequencydivision point), the two point sources may have a weak capability toreduce sound leakage. In the low-frequency band (a lower frequency banddetermined according to the frequency division point), the two pointsources may have a strong capability to reduce sound leakage. At acertain sound frequency, if the distance between the two point sourceschanges, its capability to reduce sound leakage may be changed, and thedifference between the volume of the sound heard by the user and volumeof the leaked sound may also be changed. For a better description, thecurve of a far-field leakage as a function of the distance of thetwo-point sound sources may be described with reference to FIGS. 3A and3B.

FIGS. 3A and 3B are exemplary graphs illustrating a volume of anear-field sound and a volume of a far-field leakage as a function of adistance between two point sources according to some embodiments of thepresent disclosure. FIG. 3B may be a graph generated by performing anormalization on the graph in FIG. 3A.

In FIG. 3A, a solid line may represent a variation curve of the volumeof the two point sources as a function of the distance between the twopoint sources, and the dotted line may represent the variation curve ofthe volume of the leaked sound of the two point sources as a function ofthe distance between the two point sources. The abscissa may represent adistance ratio d/d0 of the distance d of the two point sources to areference distance d0. The ordinate may represent a sound volume (theunit is decibel dB). The distance ratio d/d0 may reflect a variation ofthe distance between the two point sources. In some embodiments, thereference distance d0 may be selected within a specific range. Forexample, d0 may be a specific value in the range of 2.5 mm˜10 mm, e.g.,d0 may be 5 mm. In some embodiments, the reference distance d0 may bedetermined based on a listening position. For example, the distancebetween the listening position to the nearest point source may be takenas the reference distance d0. It should be known that the referencedistance d0may be flexibly selected from any other suitable valuesaccording to the actual conditions, which is not limited here. Merely byway of example, in FIG. 3A, d0 may be equal to 5 mm.

When the sound frequency is a constant, the volume of the sound heard bythe user and volume of the leaked sound of the two point sources mayincrease as the distance between the two point sources increases. Whenthe distance ratio d/d0 of is less than a threshold ratio, an increase(or increment) in the volume of the sound heard by the user may belarger than an increase (or increment) in the volume of the leaked soundas the distance between two point sources increases. That is to say, theincrease in volume of the sound heard by the user may be moresignificant than the increase in volume of the leaked sound. Forexample, as shown in FIG. 3A, when the distance ratio d/d0 is 2, thedifference between the volume of the sound heard by the user and thevolume of the leaked sound may be about 20 dB. When the distance ratiod/d0 is 4, the difference between the volume of the sound heard by theuser and the volume of the leaked sound may be about 25 dB. In someembodiments, when the distance ratio d/d0 reaches the threshold ratio,the ratio of the volume of the sound heard by the user to the volume ofthe leaked sound of the two point sources may reach a maximum value. Atthis time, as the distance of the two point sources further increases,the curve of the volume of the sound heard by the user and the curve ofthe volume of the leaked sound may gradually go parallel, that is, theincrease in volume of the sound heard by the user and the increase involume of the leaked sound may remain substantially the same. Forexample, as shown in FIG. 3B, when the distance ratio d/d0 is 5, 6, or7, the difference between the volume of the sound heard by the user andthe volume of the leaked sound may remain substantially the same, bothof which may be about 25 dB. That is, the increase in volume of thesound heard by the user may be the same as the increase in volume of theleaked sound. In some embodiments, the threshold ratio of the distanceratio d/d0 of the two point sources may be in the range of 0˜7. Forexample, the threshold ratio of d/d0 may be set in the range of 0.5˜4.5.As another example, the threshold ratio of d/d0 may be set in the rangeof 1˜4.

In some embodiments, the threshold ratio value may be determined basedon the variation of the difference between the volume of the sound heardby the user and the volume of the leaked sound of the two point sourcesof FIG. 3A. For example, the ratio corresponding to the maximumdifference between the volume of the sound heard by the user and thevolume of the leaked sound may be determined as the threshold ratio. Asshown in FIG. 3B, when the distance ratio d/d0 is less than thethreshold ratio (e.g., 4), a curve of a normalized sound heard by theuser may show an upward trend (the slope of the curve is larger than 0)as the distance between the two point sources increases. That is, theincrease in sound heard by the user volume may be greater than theincrease in volume of the leaked sound. When the distance ratio d/d0 isgreater than the threshold ratio, the slope of the curve of thenormalized sound heard by the user may gradually approach 0 as thedistance between the two point sources increases. That is to say, theincrease in volume of the sound heard by the user may be no longergreater than the increase in volume of the leaked sound as the distancebetween the two point sources increases.

According to the descriptions above, if the listening position is fixed,the parameters of the two point sources may be adjusted by certainmeans. It may be possible to achieve an effect that the volume of thenear-field sound has a significant increase while the volume of thefar-field leakage only increases slightly (i.e., the increase in thevolume of the near-field sound is greater than the volume of thefar-field leakage). For example, two or more sets of two point sources(such as a set of high-frequency two point sources and a set oflow-frequency two point sources) may be used. For each set, the distancebetween the point sources in the set is adjusted by a certain means, sothat the distance between the high-frequency two point sources may beless than the distance between the low-frequency two point sources. Thelow-frequency two point sources may have a small sound leakage (thecapability to reduce the sound leakage is strong), and thehigh-frequency two point sources have a large sound leakage (thecapability to reduce the sound leakage is weak). The volume of the soundheard by the user may be significantly larger than the volume of theleaked sound if a smaller distance between the two point sources is setin the high-frequency band, thereby reducing the sound leakage.

In some embodiments, each acoustic driver may have a corresponding pairof sound guiding holes. The distance between the sound guiding holescorresponding to each acoustic driver may affect the volume of thenear-field sound transmitted to the user's ears and the volume of thefar-field leakage transmitted to the environment. In some embodiments,if the distance between the sound guiding holes corresponding to ahigh-frequency acoustic driver is less than that between the soundguiding holes corresponding to a low-frequency acoustic driver, thevolume of the sound heard by the user may be increased and the soundleakage may be reduced, thereby preventing the sound from being heard byothers near the user of the acoustic output apparatus. According to theabove descriptions, the acoustic output apparatus may be effectivelyused as an open earphone even in a relatively quiet environment.

FIG. 4 is a schematic diagram illustrating an exemplary acoustic outputapparatus according to some embodiments of the present disclosure. Asshown in FIG. 4 , the acoustic output apparatus 400 may include anelectronic frequency division module 410, an acoustic driver 440, anacoustic driver 450, an acoustic route 445, an acoustic route 455, atleast two first sound guiding holes 447, and at least two second soundguiding holes 457. In some embodiments, the acoustic output apparatus400 may further include a controller (not shown in the figure). Theelectronic frequency division module 410 may be part of the controller,and configured to generate electrical signals that are input intodifferent acoustic drivers. The connection between different componentsin the acoustic output apparatus 400 may be wired and/or wireless. Forexample, the electronic frequency division module 410 may send signalsto the acoustic driver 440 and/or the acoustic driver 450 through awired transmission or a wireless transmission.

The electronic frequency division module 410 may generate one or moresignals of different frequency ranges based on a source signal. Thesource signal may come from one or more sound source apparatus (forexample, a memory storing audio data). The sound source apparatus may bepart of the acoustic output apparatus 400 or an independent device. Thesource signal may be an audio signal that is received by the acousticoutput apparatus 8400 via a wired or wireless means. In someembodiments, the electronic frequency division module 410 may decomposethe source signal into two or more frequency-divided signals havingdifferent frequencies. For example, the electronic frequency divisionmodule 410 may decompose the source signal into a firstfrequency-divided signal (or frequency-divided signal 1) having ahigh-frequency sound and a second frequency-divided signal (orfrequency-divided signal 2) having a low-frequency sound. Forconvenience, a frequency-divided signal having the high-frequency soundmay be referred to as a high-frequency signal, and a frequency-dividedsignal having the low-frequency sound may be referred to as alow-frequency signal.

For the purposes of description, a low-frequency signal described in thepresent disclosure may refer to a sound signal with a frequency in afirst frequency range (or referred to as a low frequency range). Ahigh-frequency signal may refer to a sound signal with a frequency in asecond frequency range (or referred to as a high frequency range). Thefirst frequency range and the second frequency range may or may notinclude overlapping frequency ranges. The second frequency range mayinclude frequencies higher than the first frequency range. Merely by wayof example, the first frequency range may include frequencies below afirst threshold frequency. The second frequency range may includefrequencies above a second threshold frequency. The first thresholdfrequency may be lower than the second threshold frequency, or equal tothe second threshold frequency, or higher than the second thresholdfrequency. For example, the first threshold frequency may be lower thanthe second threshold frequency (for example, the first thresholdfrequency may be 600 Hz and the second threshold frequency may be 700Hz), which means that there is no overlap between the first frequencyrange and the second frequency range. As another example, the firstthreshold frequency may be equal to the second frequency (for example,both the first threshold frequency and the second threshold frequencymay be 650 Hz or any other frequency values). As another example, thefirst threshold frequency may be higher than the second thresholdfrequency, which indicates that there is an overlap between the firstfrequency range and the second frequency range. In such cases, in someembodiments, the difference between the first threshold frequency andthe second threshold frequency may not exceed a third thresholdfrequency. The third threshold frequency may be a fixed value, forexample, 20 Hz, 50 Hz, 100 Hz, 150 Hz, or 200 Hz. Optionally, the thirdthreshold frequency may be a value related to the first thresholdfrequency and/or the second threshold frequency (for example, 5%, 10%,15%, etc., of the first threshold frequency). Alternatively, the thirdthreshold frequency may be a value flexibly set by the user according tothe actual needs, which may be not limited herein. It should be notedthat the first threshold frequency and the second threshold frequencymay be flexibly set according to different situations, and are notlimited herein.

In some embodiments, the electronic frequency division module 410 mayinclude a frequency divider 415, a signal processor 420, and a signalprocessor 430. The frequency divider 415 may be used to decompose thesource signal into two or more frequency-divided signals containingdifferent frequency components. For example, a frequency-divided signal1 having a high-frequency sound component and a frequency-divided signal2 having a low-frequency sound component. In some embodiments, thefrequency divider 415 may be any electronic device that may implementthe signal decomposition function, including but not limited to one of apassive filter, an active filter, an analog filter, a digital filter, orany combination thereof. In some embodiments, the frequency divider 415may divide the source signal based on one or more frequency divisionpoints. A frequency division point may refer to a specific frequencydistinguishing the first frequency range and the second frequency range.For example, when there is an overlapping frequency range between thefirst frequency range and the second frequency range, the frequencydivision point may be a feature point within the overlapping frequencyrange (for example, a low-frequency boundary point, a high-frequencyboundary point, a center frequency point, etc., of the overlappingfrequency range). In some embodiments, the frequency division point maybe determined according to a relationship between the frequency and thesound leakage of the acoustic output apparatus (for example, the curvesshown in FIGS. 2, 3A and 3B). For example, considering that the soundleakage of the acoustic output apparatus changes with the frequency, afrequency point corresponding to the volume of the leaked soundsatisfying a certain condition may be selected as the frequency divisionpoint. For example, 1000 Hz shown in FIG. 6 . In some alternativeembodiments, the user may specify a specific frequency as the frequencydivision point directly. For example, considering that the frequencyrange of sounds that the human ear may hear is 20 Hz-20 kHz, the usermay select a frequency point in this range as the frequency divisionpoint. For example, the frequency division point may be 600 Hz, 800 Hz,1000 Hz, 1200 Hz, or the like. In some embodiments, the frequencydivision point may be determined based on the performance of theacoustic drivers 440 and 450. The frequency division point may bedetermined based on the performance of the acoustic driver. For example,considering that a low-frequency acoustic driver and a high-frequencyacoustic driver have different frequency response curves, the frequencydivision point may be selected within a frequency range. The frequencyrange may be above ½ of the upper limiting frequency of thelow-frequency acoustic driver and below 2 times of the lower limitingfrequency of the high-frequency acoustic driver. In some embodiments,the frequency division point may be selected in a frequency range above⅓ of the upper limiting frequency of the low-frequency acoustic driverand below 1.5 times of the lower limiting frequency of thehigh-frequency acoustic driver. In some embodiments, in the overlappingfrequency range, the positional relationship between point sources mayalso affect the volume of the sound produced by the acoustic outputapparatus in the near-field and the far-field. More details may be foundin International application No. PCT/CN2019/130886, filed on Dec. 31,2019, the entire contents of which are hereby incorporated by reference.

The signal processor 420 and the signal processor 430 may furtherprocess a frequency-divided signal to meet the requirements of soundoutput. In some embodiments, the signal processor 420 and/or the signalprocessor 430 may include one or more signal processing components. Forexample, the signal processing components(s) may include, but notlimited to, an amplifier, an amplitude modulator, a phase modulator, adelayer, a dynamic gain controller, or the like, or any combinationthereof. Merely by way of example, the processing of a sound signal bythe signal processor 420 and/or the signal processor 430 may includeadjusting the amplitude of a portion of the sound signal that has aspecific frequency. In some embodiments, if the first frequency rangeand the second frequency range overlap, the signal processors 420 and430 may adjust the intensity of a portion of a sound signal that has thefrequency in the overlapping frequency range (for example, reduce theamplitude of the portion that has the frequency in the overlappingfrequency range). This may avoid that in a final sound outputted by theacoustic output apparatus, the portion that corresponds to theoverlapping frequency range may have an excessive volume caused by thesuperposition of multiple sound signals.

After being processed by the signal processors 420 or 430, thefrequency-divided signals 1 and 2 may be transmitted to the acousticdrivers 440 and 450, respectively. In some embodiments, the processedfrequency-divided signal transmitted into the acoustic driver 440 may bea sound signal having a lower frequency range (e.g., the first frequencyrange). Therefore, the acoustic driver 440 may also be referred to as alow-frequency acoustic driver. The processed frequency-divided signaltransmitted into the acoustic driver 450 may be a sound signal having ahigher frequency range (e.g., the second frequency range). Therefore,the acoustic driver 450 may also be referred to as a high-frequencyacoustic driver. The acoustic driver 440 and the acoustic driver 450 mayconvert sound signals into a low-frequency sound and a high-frequencysound, respectively, then propagate the converted signals outwards.

In some embodiments, the acoustic driver 440 may be acoustically coupledto at least two first sound guiding holes. For example, the acousticdriver 440 may be acoustically coupled to the two first sound guidingholes 447 via two acoustic routes 445. The acoustic driver 440 maypropagate sound through the at least two first sound guiding holes 447.The acoustic driver 450 may be acoustically coupled to at least twosecond sound guiding holes. For example, the acoustic driver 450 may beacoustically coupled to the two second sound guiding holes 457 via twoacoustic routes 455. The acoustic driver 450 may propagate sound throughthe at least two second sound guiding holes 457. A sound guiding holemay be a small hole formed on the acoustic output apparatus with aspecific opening and allowing sound to pass. The shape of a soundguiding hole may include but not limited to a circle shape, an ovalshape, a square shape, a trapezoid shape, a rounded quadrangle shape, atriangle shape, an irregular shape, or the like, or any combinationthereof. In addition, the number of the sound guiding holes connected tothe acoustic driver 440 or 450 may not be limited to two, which may bean arbitrary value instead, for example, three, four, six, or the like.

In some embodiments, in order to reduce the far-field leakage of theacoustic output apparatus 400, the acoustic driver 440 may be used tooutput low-frequency sounds with the same (or approximately the same)amplitude and opposite (or approximately opposite) phases via the atleast two first sound guiding holes. The acoustic driver 450 may be usedto output high-frequency sounds with the same (or approximately thesame) amplitude and opposite (or approximately opposite) phases via theat least two second sound guiding holes. In this way, the far-fieldleakage of low-frequency sounds (or high-frequency sounds) may bereduced according to the principle of acoustic destructive interference.

According to the FIG. 2 , FIG. 3A and FIG. 3B, considering that thewavelength of a low-frequency sound is longer than that of ahigh-frequency sound, and in order to reduce the destructiveinterference of the sound in the near-field (for example, near theuser's ear), the distance between the first sound guiding holes and thedistance between the second sound guiding holes may have differentvalues. For example, assuming that there is a first distance between thetwo first sound guiding holes and a second distance between the twosecond sound guiding holes, the first distance may be longer than thesecond distance. In some embodiments, the first distance and the seconddistance may be arbitrary values. Merely by way of example, the firstdistance may be longer than 40 mm. For example, in the range of 20 mm-40mm. The second distance may not be longer than 12 mm, and the firstdistance may be longer than the second distance. In some embodiments,the first distance may not be shorter than 12 mm. The second distancemay be shorter than 7 mm, for example, in the range of 3 mm-7 mm. Insome embodiments, the first distance may be 30 mm, and the seconddistance may be 5 mm. As another example, the first distance may be atleast twice longer than the second distance. In some embodiments, thefirst distance may be at least three times longer than the seconddistance. In some embodiments, the first distance may be at least 5times longer than the second distance.

As shown in FIG. 4 , the acoustic driver 440 may include a transducer443. The transducer 443 may transmit a sound to the first sound guidinghole(s) 447 through the acoustic route 445. The acoustic driver 450 mayinclude a transducer 453. The transducer 453 may transmit a sound to thesecond sound guiding hole(s) 457 through the acoustic route 855. In someembodiments, the transducer may include, but not limited to, atransducer of a gas-conducting acoustic output apparatus, a transducerof a bone-conducting acoustic output apparatus, a hydroacoustictransducer, an ultrasonic transducer, or the like, or any combinationthereof. In some embodiments, the transducer may be of a moving coiltype, a moving iron type, a piezoelectric type, an electrostatic type,or a magnetostrictive type, or the like, or any combination thereof.

In some embodiments, the acoustic drivers (such as the low-frequencyacoustic driver 440, the high-frequency acoustic driver 450) may includetransducers with different properties or different counts oftransducers. For example, each of the low-frequency acoustic driver 440and the high-frequency acoustic driver 450 may include a transducer, andthe transducers of the frequency acoustic driver 840 and thehigh-frequency acoustic driver 850 may have different frequency responsecharacteristics (such as a low-frequency speaker unit and ahigh-frequency speaker unit). As another example, the low-frequencyacoustic driver 440 may include two transducers 443 (such as two of thelow-frequency speaker units), and the high-frequency acoustic driver 450may include two transducers 453 (such as two of the high-frequencyspeaker units).

In some embodiments, the acoustic output apparatus 400 may generatesounds with different frequency ranges by other means, for example, atransducer frequency division, an acoustic route frequency division, orthe like. When the acoustic output apparatus 400 uses a transducer or anacoustic route to divide a sound, the electronic frequency divisionmodule 410 (e.g., the part inside the dotted frame in FIG. 4 ) may beomitted. The source signal may be input to the acoustic driver 440 andthe acoustic driver 450, respectively.

In some embodiments, the acoustic output apparatus 400 may use aplurality of transducers to achieve signal frequency division. Forexample, the acoustic driver 440 and the acoustic driver 450 may convertthe inputted source signal into a low-frequency signal and ahigh-frequency signal, respectively. Specifically, through thetransducer 443 (such as a low-frequency speaker), the low-frequencyacoustic driver 440 may convert the source signal into the low-frequencysound having a low-frequency component. The low-frequency sound may betransmitted to at least two first sound guiding holes 447 along at leasttwo different acoustic routes 445. Then the low-frequency sound may bepropagated outwards through the first sound guiding holes 447. Throughthe transducer 453 (such as a high-frequency speaker), thehigh-frequency acoustic driver 450 may convert the source signal intothe high-frequency sound having a high-frequency component. Thehigh-frequency sound may be transmitted to at least two second soundguiding holes 457 along at least two different acoustic routes 455. Thenthe high-frequency sound may be propagated outwards through the secondsound guiding holes 457.

In some alternative embodiments, an acoustic route (e.g., the acousticroutes 445 and the acoustic routes 455) connecting a transducer and asound guiding hole may affect the nature of the transmitted sound. Forexample, an acoustic route may attenuate or change the phase of thetransmitted sound to some extent. In some embodiments, the acousticroute may include a sound tube, a sound cavity, a resonance cavity, asound hole, a sound slit, a tuning net, or the like, or any combinationthereof. In some embodiments, the acoustic route may include an acousticimpedance material, which may have a specific acoustic impedance. Forexample, the acoustic impedance may be in the range of 5 MKS Rayleigh to500 MKS Rayleigh. Exemplary acoustic impedance materials may include butnot limited to plastic, textile, metal, permeable material, wovenmaterial, screen material or mesh material, porous material, particulatematerial, polymer material, or the like, or any combination thereof. Bysetting acoustic routes of different acoustic impedances, the soundsoutput of different transducers may be acoustically filtered. In thiscase, the sounds output through different acoustic routes have differentfrequency components.

In some embodiments, the acoustic output apparatus 400 may utilize aplurality of acoustic routes to achieve signal frequency division.Specifically, the source signal may be inputted into a specific acousticdriver and converted into a sound including high and low-frequencycomponents. The sound may be propagated along an acoustic route having aspecific frequency selection characteristic. For example, the sound maybe propagated along an acoustic route with a low-pass characteristic toa corresponding sound guiding hole to output a low-frequency sound. Inthis process, the high-frequency component of the sound may be absorbedor attenuated by the acoustic route with a low-pass characteristic.Similarly, the sound signal may be propagated along an acoustic routewith a high-pass characteristic to the corresponding sound guiding holeto output a high-frequency sound. In this process, the low-frequencycomponent of the sound may be absorbed or attenuated by the acousticroute with the high-pass characteristic.

In some embodiments, the controller in the acoustic output apparatus 400may cause the low-frequency acoustic driver 440 to output a sound in thefirst frequency range (i.e., a low-frequency sound), and cause thehigh-frequency acoustic driver 450 to output a sound in the secondfrequency range (i.e., a high-frequency sound). In some embodiments, theacoustic output apparatus 400 may also include a supporting structure.The supporting structure may be used to carry an acoustic driver (suchas the high-frequency acoustic driver 450, the low-frequency acousticdriver 440), so that the acoustic driver may be positioned away from theuser's ear. In some embodiments, the sound guiding hole(s) acousticallycoupled with the high-frequency acoustic driver 450 may be locatedcloser to an expected position of the user's ears (for example, the earcanal entrance), while the sound guiding hole(s) acoustically coupledwith the low-frequency acoustic driver 440 may be located further awayfrom the expected position. In some embodiments, the supportingstructure may be used to package the acoustic driver. For example, thesupporting structure may include a housing made of various materialssuch as plastic, metal, and tape. The housing may encapsulate theacoustic driver and form a front chamber and a rear chambercorresponding to the acoustic driver. The front chamber may beacoustically coupled to one of the at least two sound guiding holescorresponding to the acoustic driver. The rear chamber may beacoustically coupled to the other of the at least two sound guidingholes corresponding to the acoustic driver. For example, the frontchamber of the low-frequency acoustic driver 440 may be acousticallycoupled to one of the at least two first sound guiding holes 447. Therear chamber of the low-frequency acoustic driver 440 may beacoustically coupled to the other of the at least two first soundguiding holes 447. The front chamber of the high-frequency acousticdriver 450 may be acoustically coupled to one of the at least two secondsound guiding holes 457. The rear chamber of the high-frequency acousticdriver 450 may be acoustically coupled to the other of the at least twosecond sound guiding holes 457. In some embodiments, a sound guidinghole (such as the first sound guiding hole(s) 447 and the second soundguiding hole(s) 457) may be disposed on the housing.

The above description of the acoustic output apparatus 400 may be merelyprovided by way of example. Those skilled in the art may makeadjustments and changes to the structure, quantity, etc., of theacoustic driver, which is not limiting in the present disclosure. Insome embodiments, the acoustic output apparatus 400 may include anynumber of the acoustic drivers. For example, the acoustic outputapparatus 400 may include two groups of the high-frequency acousticdrivers 450 and two groups of the low-frequency acoustic drivers 440, orone group of the high-frequency acoustic drives 450 and two groups ofthe low-frequency acoustic drivers 440, and thesehigh-frequency/low-frequency drivers may be used to generate a sound ina specific frequency range, respectively. As another example, theacoustic driver 440 and/or the acoustic driver 450 may include anadditional signal processor. The signal processor may have the samestructural component as or different structural components from thesignal processor 420 or 430.

It should be noted that the acoustic output apparatus and its modulesshown in FIG. 4 may be implemented in various ways. For example, in someembodiments, the system and the modules may be implemented by hardware,software, or a combination of both. The hardware may be implemented by adedicated logic. The software may be stored in a storage that may beexecuted by a suitable instruction execution system, for example, amicroprocessor or dedicated design hardware. It will be appreciated bythose skilled in the art that the above methods and systems may beimplemented by computer-executable instructions and/or embedded in thecontrol codes of a processor. For example, the control codes may beprovided by a medium such as a disk, a CD or a DVD-ROM, a programmablememory device, such as read-only memory (e.g., firmware), or a datacarrier such as an optical or electric signal carrier. The system andthe modules in the present disclosure may be implemented not only by ahardware circuit in a programmable hardware device in an ultra largescale integrated circuit, a gate array chip, a semiconductor such alogic chip or a transistor, a field-programmable gate array, or aprogrammable logic device. The system and the modules in the presentdisclosure may also be implemented by software to be performed byvarious processors, and further also by a combination of hardware andsoftware (e.g., firmware).

It should be noted that the above description of the acoustic outputapparatus 400 and its components is only for the convenience ofdescription, and not intended to limit the scope of the presentdisclosure. It may be understood that, for those skilled in the art,after understanding the principle of the apparatus, it is possible tocombine each unit or form a substructure to connect with other unitsarbitrarily without departing from this principle. For example, theelectronic frequency division module 410 may be omitted, and thefrequency division of the source signal may be implemented by theinternal structure of the low-frequency acoustic driver 440 and/or thehigh-frequency acoustic driver 450. As another example, the signalprocessor 420 or 430 may be a part independent of the electronicfrequency division module 410. Those modifications may fall within thescope of the present disclosure.

FIGS. 5A and 5B are schematic diagrams illustrating exemplary acousticoutput apparatuses according to some embodiments of the presentdisclosure. For the purpose of illustration, sounds outputted bydifferent sound guiding holes coupled with the same transducer may bedescribed as an example. In FIGS. 5A and 5B, each transducer may have afront side and a rear side, and corresponding front chamber (i.e., thefirst acoustic route) and rear chamber (i.e., the second acoustic route)may exist on the front and rear side of the transducer, respectively. Insome embodiments, these structures may have the same or approximatelythe same equivalent acoustic impedance, such that the transducer may beloaded symmetrically. The symmetrical load of the transducer may formsound sources satisfy an amplitude and phase relationship at differentsound guiding holes (such as the “two-point sound source” having thesame amplitude and opposite phases as described above), such that aspecific sound field may be formed in the high-frequency range and/orthe low-frequency range (for example, the near-field sound may beenhanced and the far-field leakage may be suppressed).

As shown in FIGS. 5A and 5B, an acoustic output apparatus (for example,the acoustic output apparatus 500A or 500B) may include transducers, andacoustic routes and sound guiding holes connected to the transducer. Inorder to describe the actual application scenarios of an actualapplication scenario of the acoustic output apparatus more clearly, theposition of a user's ear E is shown in FIGS. 5A and 5B for explanation.FIG. 5A illustrates an application scenario of the acoustic outputapparatus 500A. The acoustic output apparatus 500A may include atransducer 543 (or referred to as a low-frequency acoustic driver), andthe transducer 543 may be coupled with two first sound guiding holes 547through an acoustic route 545. FIG. 5B illustrates an applicationscenario of the acoustic output apparatus 500B. The acoustic outputapparatus 500B may include a transducer 553 (or referred to as ahigh-frequency acoustic driver), and the transducer 553 may be coupledwith two second sound guiding holes 557 through an acoustic route 555.

The transducer 543 or 553 may vibrate under the driving of an electricsignal, and the vibration may generate sounds with equal amplitudes andopposite phases (180 degrees inversion). The type of transducer mayinclude, but not limited to, one of an air conduction speaker, a boneconduction speaker, a hydroacoustic transducer, an ultrasonictransducer, or the like, or any combination thereof. The transducer maybe of a moving coil type, a moving iron type, a piezoelectric type, anelectrostatic type, a magnetostrictive type, or the like, or anycombination thereof. In some embodiments, the transducer 543 or 553 mayinclude a vibration diaphragm, which may vibrate when driven by anelectrical signal, and the front and rear sides of the vibrationdiaphragm may simultaneously output a normal-phase sound and areverse-phase sound. In FIGS. 5A and 5B, “+” and “−” may be used torepresent sounds with different phases, wherein “+” may represent anormal-phase sound, and “−” may represent a reverse-phase sound.

In some embodiments, a transducer may be enclosed by a housing of asupporting structure, and the interior of the housing may be providedwith sound channels connected to the front and rear sides of thetransducer, respectively, thereby forming an acoustic route. Forexample, a front cavity of the transducer 543 may be coupled to one ofthe two first sound guiding holes 547 through a first acoustic route(i.e., a half of the acoustic route 545), and a rear cavity of thetransducer 543 may acoustically be coupled to the other sound guidinghole of the two first sound guiding holes 547 through a second acousticroute (i.e., the other half of the acoustic route 545). A normal-phasesound and a reverse-phase sound output from the transducer 543 may beoutput from the two first sound guiding holes 547, respectively. Asanother example, a front cavity of the transducer 553 may be coupled toone of the two sound guiding holes 557 through a third acoustic route(i.e., a half of the acoustic route 555), and a rear cavity of thetransducer 553 may be coupled to another sound guiding hole of the twosecond sound guiding holes 557 through a fourth acoustic route (i.e.,the other half of the acoustic route 555). A normal-phase sound and areverse-phase sound output from the transducer 553 may be output fromthe two second sound guiding holes 557, respectively.

In some embodiments, an acoustic route may affect the nature of thetransmitted sound. For example, an acoustic route may attenuate orchange the phase of the transmitted sound to some extent. In someembodiments, the acoustic route may include one or more of a sound tube,a sound cavity, a resonance cavity, a sound hole, a sound slit, a tuningnet, or the like, or any combination thereof. In some embodiments, theacoustic route may include an acoustic impedance material, which mayhave a specific acoustic impedance. For example, the acoustic impedancemay be in the range of 5 MKS Rayleigh to 500 MKS Rayleigh. In someembodiments, the acoustic impedance material may include but not limitedto plastics, textiles, metals, permeable materials, woven materials,screen materials, and mesh materials, or the like, or any combinationthereof. In some embodiments, in order to prevent the sound transmittedby the acoustic driver's front chamber and rear chamber from beingdifferently disturbed, the front chamber and rear chamber correspondingto the acoustic driver may have the approximately same equivalentacoustic impedance. Additionally, sound guiding holes with the sameacoustic impedance material, the same size and/or shape, etc., may beused.

The distance between the two first sound guiding holes 547 of thelow-frequency acoustic driver may be expressed as d1 (i.e., the firstdistance). The distance between the two second sound guiding holes 557of the high-frequency acoustic driver may be expressed as d2 (i.e., thesecond distance). By setting the distances d1 and d2, a higher soundvolume output in the low-frequency band and a stronger ability to reducethe sound leakage in the high-frequency band may be achieved. Forexample, the distance between the two first sound guiding holes 547 isgreater than the distance between the two second sound guiding holes 557(i.e., d1>d2).

In some embodiments, the transducer 543 and the transducer 553 may behoused together in a housing of an acoustic output apparatus, and beplaced in isolation in a structure of the housing.

In some embodiments, the acoustic output apparatus may include multiplesets of high-frequency acoustic drivers and low-frequency acousticdrivers. For example, the acoustic output apparatus may include a set ofhigh-frequency acoustic drivers and a set of low-frequency acousticdrivers for simultaneously outputting sound to the left and/or rightears. As another example, the acoustic output apparatus may include twosets of high-frequency acoustic drivers and two sets of low-frequencyacoustic drivers, wherein one set of high-frequency acoustic drivers andone set of low-frequency acoustic drivers may be used to output sound toa user's left ear, and the other set of high-frequency acoustic driversand the other set of ow-frequency acoustic drivers may be used to outputsound to a user's right ear.

In some embodiments, the high-frequency acoustic driver and thelow-frequency acoustic driver may have different powers. In someembodiments, the low-frequency acoustic driver may have a first power,the high-frequency acoustic driver may have a second power, and thefirst power may be greater than the second power. In some embodiments,the first power and the second power may be arbitrary values.

FIGS. 6A and 6B are schematic diagrams illustrating exemplary acousticoutput apparatuses 600A and 600B according to some embodiments of thepresent disclosure.

In some embodiments, the acoustic output apparatus may generate soundsin the same frequency range through two or more transducers, and thesounds may propagate outwards through different sound guiding holes. Insome embodiments, different transducers may be controlled by the samecontroller or different controllers, respectively, and may producesounds that satisfy a certain phase and amplitude condition (forexample, sounds with the same amplitude but opposite phases, sounds withdifferent amplitudes and opposite phases, etc.). For example, acontroller may make the electrical signals input into two low-frequencytransducers of an acoustic driver have the same amplitude and oppositephases. In this way, the two low-frequency transducers may outputlow-frequency sounds with the same amplitude but opposite phases.

Specifically, the two transducers in an acoustic driver (such as alow-frequency acoustic driver 610 or a high-frequency acoustic driver620) may be arranged side by side in an acoustic output apparatus, oneof which may be used to output a normal-phase sound, and the other maybe used to output a reverse-phase sound. As shown in FIG. 6A, theacoustic driver 610 may include two transducers 443, two acoustic routes445, and two first sound guiding holes 447. The acoustic driver 620 mayinclude two transducers 453, two acoustic routes 455, and two secondsound guiding holes 457. Driven by electrical signals with oppositephases, the two transducers 443 may generate a set of low-frequencysounds with opposite phases (180 degrees inversion). One of the twotransducers 443 may (such as the transducer located below) may output anormal-phase sound, and the other (such as the transducer located above)may output a reverse-phase sound. The two low-frequency sounds withopposite phases may be transmitted to the two first sound guiding holes447 along the two acoustic routes 445, respectively, and propagateoutwards through the two first sound guiding holes 447. Similarly,driven by electrical signals with opposite phases, the two transducers453 may generate a set of high-frequency sounds with opposite phases(180 degrees inversion). One of the two transducers 453 (such as thetransducer located below) may output a normal-phase high-frequencysound, and the other (such as the transducer located above) may output areverse-phase high-frequency sound. The high-frequency sounds withopposite phases may be transmitted to the two second sound guiding holes457 along the two acoustic routes 455, respectively, and propagateoutwards through the two second sound guiding holes 457.

In some embodiments, the two transducers in an acoustic driver (forexample, the low-frequency acoustic driver 610 and the high-frequencyacoustic driver 620) may be arranged relatively close to each otheralong the same straight line, and one of them may be used to output anormal-phase sound and the other may be used to output a reverse-phasesound. As shown in FIG. 6B, the left side may be the acoustic driver610, and the right side may be the acoustic driver 620. The twotransducers 443 of the acoustic driver 610 may generate a set oflow-frequency sounds of equal amplitude and opposite phases under thecontrol of the controller, respectively. One of the transducers 443 mayoutput a normal-phase low-frequency sound, and transmit the normallow-frequency sound along a first acoustic route to a first soundguiding hole 447. The other transducer 443 may output a reverse-phaselow-frequency sound, and transmit the reverse-phase low-frequency soundalong a second acoustic route to another first sound guiding hole 447.The two transducers 453 of the acoustic driver 620 may generatehigh-frequency sound of equal amplitude and opposite phases under thecontrol of the controller, respectively. One of the transducers 453 mayoutput a normal-phase high-frequency sound, and transmit thenormal-phase high-frequency sound along a third acoustic route to asecond sound guiding hole 457. The other transducer 453 may output areverse-phase high-frequency sound, and transmit the reverse-phasehigh-frequency sound along a fourth acoustic route to another secondsound guiding hole 457.

In some embodiments, the transducer 443 and/or the transducer 453 may beof various suitable types. For example, the transducer 443 and thetransducer 453 may be dynamic coil speakers, which may have thecharacteristics of a high sensitivity in low-frequency, a deep lowfrequency depth, and a small distortion. As another example, thetransducer 443 and the transducer 453 may be moving iron speakers, whichmay have the characteristics of a small size, a high sensitivity, and alarge high-frequency range. As another example, the transducers 443 and453 may be air-conducted speakers, or bone-conducted speakers. Asanother example, the transducer 443 and the transducer 453 may bebalanced armature speakers. In some embodiments, the transducer 443 andthe transducer 453 may be of different types. For example, thetransducer 443 may be a moving iron speaker, and the transducer 453 maybe a moving coil speaker. As another example, the transducer 443 may bea dynamic coil speaker, and the transducer 453 may be a moving ironspeaker.

In FIGS. 6A-6B, the distance between the two-point sound sources of theacoustic driver 610 may be d1, the distance between the two-point soundsources of the acoustic driver 620 may be d2, and d1 may be greater thand2. As shown in FIG. 6B, the listening position (that is, the positionof the ear canal when the user wears an acoustic output apparatus) maybe approximately located on a line of a set of two-point sound sources.In some embodiments, the listening position may be located at anysuitable position. For example, the listening position may be located ona circle centered on the center point of the two-point sound source. Foranother example, the listening position may be on the same side of twosets two-point sound sources connection, or in the middle of the twosets two-point sound sources connection.

It may be understood that the simplified structure of the acousticoutput apparatus shown in FIGS. 6A-6B may be merely by way of example,which may be not a limitation for the present disclosure. In someembodiments, the acoustic output apparatus may include a supportingstructure, a controller, a signal processor, or the like, or anycombination thereof.

FIGS. 7A-7B are schematic diagrams illustrating exemplary acousticoutput apparatuses 700A and 700B according to some embodiments of thepresent disclosure.

In some embodiments, acoustic drivers (e.g., acoustic drivers 610 or620) may include multiple narrow-band speakers. As shown in FIG. 7A, theacoustic output apparatus 700A may include a plurality of narrow-bandspeaker units and a signal processing module. On the left or right sideof the user, the acoustic output apparatus 700A may include n groups,narrow-band speaker units, respectively. Each group of narrow-bandspeaker units may have different frequency response curves, and thefrequency response of each group may be complementary and collectivelycover the audible sound frequency band. A narrow-band speaker unit usedherein may be an acoustic driver with a narrower frequency responserange than a low-frequency acoustic driver and/or a high-frequencyacoustic driver. Taking the speaker units located on the left side ofthe user as shown in FIG. 7A as an example: A1˜An and B1˜Bn form ngroups of two-point sound sources. When the same electrical signal isinput, each two-point sound source may generate sounds with differentfrequency ranges. By setting the distance of each two-point soundsource, the near-field and far-field sound of each frequency band may beadjusted. For example, in order to enhance the volume of near-fieldsound and reduce the volume of far-field leakage, the distance between apair of two point sources corresponding to a high frequency may be lessthan the distance between a pair of two point sources corresponding to alow frequency.

In some embodiments, the signal processing module may include anEqualizer (EQ) processing module and a Digital Signal Processor (DSP)processing module. The signal processing module may be used to implementsignal equalization and other digital signal processing algorithms (suchas amplitude modulation and phase modulation). The processed signal maybe connected to a corresponding acoustic driver (for example, anarrow-band speaker unit) to output a sound. Preferably, a narrow-bandspeaker unit may be a dynamic coil speaker or a moving iron speaker. Insome embodiments, the narrow-band speaker unit may be a balancedarmature speaker. Two-point sound sources may be constructed using twobalanced armature speakers, and the sound output from the two speakersmay be in opposite phases.

In some embodiments, an acoustic driver (such as acoustic drivers 440,450, 610 or 620) may include multiple sets of full-band speakers. Asshown in FIG. 7B, the acoustic output apparatus 700B may include aplurality of sets of full-band speaker units and a signal processingmodule. On the left or right side of the user, the acoustic outputapparatus may include n groups full-band speaker units, respectively.Each full-band speaker unit may have the same or similar frequencyresponse curve and may cover a wide frequency range.

Taking the speaker units located on the left side of the user as shownin FIG. 7B as an example: A1˜An and B1˜Bn form n two-point soundsources. The difference between FIGS. 7A and 7B may be that the signalprocessing module in FIG. 7B may include at least one set of filters forperforming frequency division on the sound source signal to generateelectric signals corresponding to different frequency ranges, and theelectric signals corresponding to different frequency ranges may beinput into each group of full-band speaker units. In this way, eachgroup of speaker units (similar to the two-point sound source) mayproduce sounds with different frequency ranges separately.

FIGS. 8A-8C are schematic diagrams illustrating an acoustic routeaccording to some embodiments of the present disclosure.

As described above, an acoustic filtering network may be constructed bysetting structures such as a sound tube, a sound cavity, and a soundresistance in an acoustic route to achieve frequency division of sound.FIGS. 8A-8C show schematic structural diagrams of frequency division ofa sound signal using an acoustic route. It should be noted that FIGS.8A-8C may be examples of setting the acoustic route when using theacoustic route to perform frequency division on the sound signal and maynot be a limitation on the present disclosure.

As shown in FIG. 8A, an acoustic route may be composed of one or moregroups of lumen structures connected in series, and an acousticimpedance material may be provided in the lumen structures to adjust theacoustic impedance of the entire structure to achieve a filteringeffect. In some embodiments, a band-pass filtering or a low-passfiltering may be performed on the sound by adjusting the size of thelumen structures and/or the acoustic impedance material to achievefrequency division of the sound. As shown in FIG. 8B, a structure withone or more sets of resonant cavities (for example, Helmholtz cavity)may be constructed on a branch of the acoustic route, and the filteringeffect may be achieved by adjusting the size of each structure and theacoustic impedance material. As shown in FIG. 8C, a combination of alumen structure and a resonant cavity (for example, a Helmholtz cavity)structure may be constructed in an acoustic route, and a filteringeffect may be achieved by adjusting the size of the lumen structureand/or a resonant cavity, and/or the acoustic impedance material.

FIG. 9 shows a curve of sound leakage of an acoustic output apparatus(for example, the acoustic output apparatus 400) under the action of twosets of two-point sound sources (a set of high-frequency two-point soundsources and a set of low-frequency two-point sound sources). Thefrequency division points of the two sets of two-point sound sources maybe around 700 Hz.

A normalization parameter a may be used to evaluate the volume of theleaked sound (descriptions of a may be found in Equation (4)). As shownin FIG. 9 , compared with a single point source, the two sets of twopoint sources may have a stronger ability to reduce sound leakage. Inaddition, compared with the acoustic output apparatus provided with onlyone set of two point sources, the two sets of two point sources mayoutput high-frequency sounds and low-frequency sounds, separately. Thedistance between the low-frequency two point sources may be greater thanthat of the high-frequency two point sources. In the low-frequencyrange, by setting a larger distance (d1) between the low frequency twopoint sources, the increase in the volume of the near-field sound may begreater than the increase in the volume of the far-field leakage, whichmay achieve a higher volume of the near-field sound output in thelow-frequency band. At the same time, in the low-frequency range,because that the sound leakage of the low frequency two point sources isvery small, increasing the distance d1 may slightly increase the soundleakage. In the high-frequency range, by setting a small distance (d2)between the high frequency two point sources, the problem that thecutoff frequency of high-frequency sound leakage reduction is too lowand the audio band of the sound leakage reduction is too narrow may beovercome. Therefore, by setting the distance d1 and/or the distance d2,the acoustic output apparatus provided in the embodiments of the presentdisclosure may obtain a stronger sound leakage suppressing capabilitythan an acoustic output apparatus having a single point source or asingle set of two point sources.

In some embodiments, affected by factors such as the filtercharacteristic of a circuit, the frequency characteristic of atransducer, and the frequency characteristic of an acoustic route, theactual low-frequency and high-frequency sounds of the acoustic outputapparatus may differ from those shown in FIG. 9 . In addition,low-frequency and high-frequency sounds may have a certain overlap(aliasing) in the frequency band near the frequency division point,causing the total sound leakage reduction of the acoustic outputapparatus not have a mutation at the frequency division point as shownin FIG. 9 . Instead, there may be a gradient and/or a transition in thefrequency band near the frequency division point, as shown by a thinsolid line in FIG. 9 . It may be understood that these differences maynot affect the overall leakage reduction effect of the acoustic outputapparatus provided by the embodiments of the present disclosure.

According to FIGS. 4 to 9 and the related descriptions, the acousticoutput apparatus provided by the present disclosure may be used tooutput sounds in different frequency bands by setting high-frequency twopoint sources and low-frequency two point sources, thereby achieving abetter acoustic output effect. In addition, by setting different sets oftwo point sources with different distances, the acoustic outputapparatus may have a stronger capability to reduce the sound leakage ina high frequency band, and meet the requirements of an open acousticoutput apparatus.

In some alternative embodiments, an acoustic output apparatus mayinclude at least one acoustic driver, and the sound generated by the atleast one acoustic driver may propagate outwards through at least twosound guiding holes coupled with the at least one acoustic driver. Insome embodiments, the acoustic output apparatus may be provided with abaffle structure, so that the at least two sound guiding holes may bedistributed on two sides of the baffle. In some embodiments, the atleast two sound guiding holes may be distributed on both sides of theuser's auricle. At this time, the auricle may serve as a baffle thatseparates the at least two sound guiding holes, so that the at least twosound guiding holes may have different acoustic routes to the user's earcanal. More descriptions of two point sources and a baffle may be foundin International applications No. PCT/CN2019/130921 and No.PCT/CN2019/130942, both filed on Dec. 31, 2019, the entire contents ofeach of which are hereby incorporated by reference in the presentdisclosure.

FIG. 10 is a schematic diagram illustrating another exemplary acousticoutput apparatus according to some embodiments of the presentdisclosure. As shown in FIG. 10 , the acoustic output apparatus 1000 mayinclude a supporting structure 1010 and an acoustic driver 1020 mountedwithin the supporting structure. In some embodiments, an acoustic outputapparatus 1000 may be worn on the user's body (for example, the humanbody's head, neck, or upper torso) through a supporting structure 1010.At the same time, the supporting structure 1010 and the acoustic driver1020 may approach but not block the ear canal, so that the user's earmay remain open, while the user may hear both the sound output from theacoustic output apparatus 1000 and the external environment. Forexample, the acoustic output apparatus 1000 may be arranged around orpartially around the user's ear, and transmit sounds by means of airconduction or bone conduction.

The supporting structure 1010 may be used to be worn on the user's bodyand include one or more acoustic drivers 1020. In some embodiments, thesupporting structure 1010 may have an enclosed housing structure with ahollow interior, and the one or more acoustic drivers 1020 may belocated inside the supporting structure 1010. In some embodiments, theacoustic output apparatus 1000 may be combined with a product, such asglasses, a headset, a display apparatus, an AR/VR helmet, etc. In thiscase, the supporting structure 1010 may be fixed near the user's ear ina hanging or clamping manner. In some alternative embodiments, a hookmay be provided on the supporting structure 1010, and the shape of thehook may match the shape of the user's auricle, so that the acousticoutput apparatus 1000 may be independently worn on the user's earthrough the hook. The acoustic output apparatus 1000 may communicatewith a signal source (for example, a computer, a mobile phone, or othermobile devices) in a wired or wireless manner (for example, Bluetooth).For example, the acoustic output apparatus 1000 at the left and rightears may be directly in communication connection with the signal sourcein a wireless manner. As another example, the acoustic output apparatus1000 at the left and right ears may include a first output apparatus anda second output apparatus. The first output apparatus may be incommunication connection with the signal source, and the second outputapparatus may be wirelessly connected with the first output apparatus.The audio output of the first output apparatus and the second outputapparatus may be synchronized through one or more synchronizationsignals. A wireless connection disclosed herein may include but notlimited to Bluetooth, a local area network, a wide area network, awireless personal area network, a near-field communication, or the like,or any combination thereof.

In some embodiments, the supporting structure 1010 may have a housingstructure with a shape suitable for human ears, for example, a circularring, an oval, a polygonal (regular or irregular), a U-shape, a V-shape,a semi-circle, so that the supporting structure 1010 may be directlyhooked at the user's ear. In some embodiments, the supporting structure1010 may include one or more fixed structures. The fixed structure(s)may include an ear hook, a head strip, or an elastic band, so that theacoustic output apparatus 1000 may be better fixed on the user,preventing the acoustic output apparatus 1000 from falling down. Merelyby way of example, the elastic band may be a headband to be worn aroundthe head region. As another example, the elastic band may be a neckbandto be worn around the neck/shoulder region. In some embodiments, theelastic band may be a continuous band and be elastically stretched to beworn on the user's head. In the meanwhile, the elastic band may alsoexert pressure on the user's head so that the acoustic output apparatus1000 may be fixed to a specific position on the user's head. In someembodiments, the elastic band may be a discontinuous band. For example,the elastic band may include a rigid portion and a flexible portion. Therigid portion may be made of a rigid material (for example, plastic ormetal), and the rigid portion may be fixed to the supporting structure1010 of the acoustic output apparatus 1000 by a physical connection. Theflexible portion may be made of an elastic material (for example, cloth,composite, or/and neoprene).

In some embodiments, when the user wears the acoustic output apparatus1000, the supporting structure 1010 may be located above or below theauricle. The supporting structure 1010 may be provided with a soundguiding hole 1011 and a sound guiding hole 1012 for transmitting sound.In some embodiments, the sound guiding hole 1011 and the sound guidinghole 1012 may be located on both sides of the user's auricle,respectively, and the acoustic driver 1020 may output sounds through thesound guiding hole 1011 and the sound guiding hole 1012.

The acoustic driver 1020 may be a component that may receive anelectrical signal, and convert the electrical signal into a sound signalfor output. In some embodiments, in terms of frequency, the type of theacoustic driver 1020 may include a low-frequency acoustic driver, ahigh-frequency acoustic driver, or a full-frequency acoustic driver, orany combination thereof. In some embodiments, the acoustic driver 1020may include a moving coil, a moving iron, a piezoelectric, anelectrostatic, a magnetostrictive driver, or the like, or a combinationthereof.

In some embodiments, the acoustic driver 1020 may include a vibrationdiaphragm. When the vibration diaphragm vibrates, sounds may betransmitted from the front and rear sides of the vibration diaphragm,respectively. In some embodiments, the front side of the vibrationdiaphragm in the supporting structure 1010 may be provided with a frontchamber 1013 for transmitting sound. The front chamber 1013 may beacoustically coupled with the sound guiding hole 1011. The sound on thefront side of the vibration diaphragm may be outputted from the soundguiding hole 1011 through the front chamber 1013. The rear side of thevibration diaphragm in the supporting structure 1010 may be providedwith a rear chamber 1014 for transmitting sound. The rear chamber 1014may be acoustically coupled with the sound guiding hole 1012. The soundon the rear side of the vibration diaphragm may be outputted from thesound guiding hole 1012 through the rear chamber 1014. It should benoted that, when the vibration diaphragm is vibrating, the front sideand the rear side of the vibration diaphragm may simultaneously generatesounds with opposite phases. After passing through the front chamber1013 and rear chamber 1014, respectively, the sounds may propagateoutward from the sound guiding hole 1011 and the sound guiding hole1012, respectively. In some embodiments, by adjusting the structure ofthe front chamber 1013 and the rear chamber 1014, the sounds output bythe acoustic driver 1020 at the sound guiding hole 1011 and the soundguiding hole 1012 may meet specific conditions. For example, bydesigning the lengths of the front chamber 1013 and the rear chamber1014, the sound guiding hole 1011 and the sound guiding hole 1012 mayoutput sounds with a specific phase relationship (for example, oppositephases). Therefore, the problems including a small volume of the soundheard by the user in the near-field of the acoustic output apparatus1000 and a large sound leakage in the far-field of the acoustic outputapparatus 1000 may be effectively resolved.

In some alternative embodiments, the acoustic driver 1020 may alsoinclude a plurality of vibration diaphragms (e.g., two vibrationdiaphragms). Each of the plurality of vibration diaphragms may vibrateto generate a sound, which may pass through a cavity connected to thevibration diaphragm in the supporting structure, and output fromcorresponding sound guiding hole(s). The plurality of vibrationdiaphragms may be controlled by the same controller or differentcontrollers and generate sounds that satisfy certain phase and amplitudeconditions (for example, sounds of the same amplitude but oppositephases, sounds of different amplitudes and opposite phases, etc.).

As mentioned above, with a certain sound frequency, as the distancebetween two point sources increases, the volume of the sound heard bythe user and the volume of the leaked sound corresponding to the twopoint sources may increase. For a clearer description, the relationshipbetween volume of the sound heard by the user, the volume of soundleakage, and the point source distance d may be further explained inconnection with FIGS. 11 through 13 .

FIG. 11 is a schematic diagram illustrating two points of sound sourcesand a listening position according to some embodiments of the presentdisclosure. As shown in FIG. 11 , a point source a1 and a point sourcea2 may be on the same side of the listening position. The point sourcea1 may be closer to the listening position, and the point source a1 andthe point source a2 may output sounds with the same amplitude butopposite phases.

FIG. 12 is a graph illustrating a variation of the volume of the soundheard by the user of two-point sound sources with different distances asa function of a frequency of sound according to some embodiments of thepresent disclosure. The abscissa may represent the frequency (f) of thesound output by the two-point sound source (denoted as a1 and a2), andthe unit may be hertz (Hz). The ordinate may represent the volume of thesound, and the unit may be decibel (dB). As shown in FIG. 12 , as thedistance between the point source a1 and the point source a2 graduallyincreases (for example, from d to 10d), the sound volume at thelistening position may gradually increase. That is, as the distancebetween the point source a1 and the point source a2 increases, thedifference in sound pressure amplitude (i.e., sound pressure difference)between the two sounds reaching the listening position may becomelarger, making the sound cancellation effect weaker, which may increasethe sound volume at the listening position. However, due to theexistence of sound cancellation, the sound volume at the listeningposition may still be less than the sound volume generated by a singlepoint source at the same position in the low and middle frequency band(for example, a frequency of less than 1000 Hz). However, in thehigh-frequency band (for example, a frequency close to 10000 Hz), due tothe decrease in the wavelength of the sound, mutual enhancement of thesound may appear, making the sound generated by the two point sourceslouder than that of the single point source. In some embodiments, asound pressure may refer to the pressure generated by the sound throughthe vibration of the air.

In some embodiments, by increasing the distance of the two-point soundsources (for example, the point sound source a1 and the point soundsource a2), the sound volume at the listening position may be increased.But as the distance increases, the sound cancellation of the two-pointsound sources may become weaker, which may lead to an increase of thefar-field sound leakage. For illustration purposes, FIG. 13 is a graphillustrating a variation of a normalized parameter of differentdistances between two-point sound sources in the far-field along with afrequency of sound according to some embodiments of the presentdisclosure. The abscissa may represent the frequency (f) of the sound,the unit may be Hertz (Hz). The ordinate may use a normalizationparameter a for evaluating the volume of the leaked sound, and the unitmay be decibel (dB). As shown in FIG. 13 , taking the normalizationparameter a of a single-point sound source as a reference, as thedistance of the two-point sound sources increases from d to 10d, thenormalization parameter a may gradually increase, indicating that thesound leakage may gradually increase. More descriptions regarding thenormalization parameter a may be found in equation (4) and relateddescriptions.

In some embodiments, adding a baffle structure to the acoustic outputapparatus may be beneficial to improve the output effect of the acousticoutput apparatus, that is, to increase the sound intensity at thenear-field listening position, while reducing the volume of thefar-field sound leakage. For illustration, FIG. 14 is a diagramillustrating an exemplary baffle provided between two-point soundsources according to some embodiments of the present disclosure. Asshown in FIG. 14 , when a baffle is provided between the point soundsource a1 and the point sound source a2, in the near-field, the soundwave of the point sound source a2 may need to bypass the baffle tointerfere with the sound wave of the point sound source a1 at thelistening position, which may be equivalent to increasing the length ofthe acoustic route from the point sound source a2 to the listeningposition. Therefore, assuming that the point sound source a1 and thepoint sound source a2 have the same amplitude, compared to the casewithout a baffle, the difference in the amplitude of the sound waves ofthe point sound source a1 and the point sound source a2 at the listeningposition may increase, so that the degree of cancellation of the twosounds at the listening position may decrease, causing the sound volumeat the listening position to increase. In the far-field, because thesound waves generated by the point sound source a1 and the point soundsource a2 do not need to bypass the baffle in a large space, the soundwaves may interfere (similar to the case without a baffle). Compared tothe case without a baffle, the sound leakage in the far-field may notincrease significantly. Therefore, a baffle structure being providedbetween the point sound source a1 and the point sound source a2 mayincrease the sound volume at the near-field listening positionsignificantly when the far-field leakage volume does not increasesignificantly.

In the present disclosure, when the two-point sound sources are locatedon both sides of the auricle, the auricle may serve as a baffle, so theauricle may also be referred to as a baffle for convenience. As anexample, due to the existence of the auricle, the result may beequivalent to that the near-field sound may be generated by two-pointsound sources with a distance of D1 (also known as mode 1). Thefar-field sound may be generated by two-point sound sources with adistance of D2 (also known as mode 2), and D1>D2. FIG. 15 is a graphillustrating a variation of the volume of a sound heard by a user as afunction of the frequency of sound when the auricle is located betweentwo point sources according to some embodiments of the presentdisclosure. As shown in FIG. 15 , when the frequency is low (forexample, when the frequency is less than 1000 Hz), the volume at thenear-field sound (that is, the sound heard by the user by the user'sear) may basically be the same as that of the near-field sound in mode1, be greater than the volume of the near-field sound in mode 2, and beclose to the volume of the near-field sound of a single point source. Asthe frequency increases (for example, when the frequency is between 2000Hz and 7000 Hz), the volume of the near-field sound when mode 1 and thetwo-point sound sources being distributed on both sides of the auriclemay be greater than that of the one-point sound source. It shows thatwhen the user's auricle is located between the two-point sound sources,the volume of the near-field sound transmitted from the sound source tothe user's ear may be effectively enhanced. FIG. 16 is a graphillustrating a variation of the volume of a leaked sound as a functionof the frequency of sound when the auricle is located between two pointsources according to some embodiments of the present disclosure. Asshown in FIG. 16 , as the frequency increases, the volume of thefar-field leakage may increase. When the two-point sound sources aredistributed on both sides of the auricle, the volume of the far-fieldleakage generated by the two-point sound sources may be basically thesame as the volume of the far-field leakage of Mode 2, and both of whichmay be less than the volume of the far-field leakage of Mode 1 and thevolume of the far-field leakage of a single-point sound source. It showsthat when the user's auricle is located between the two-point soundsource, the sound transmitted from the sound source to the far-field maybe effectively reduced, that is, the sound leakage from the sound sourceto the surrounding environment may be effectively reduced. FIG. 17 is agraph illustrating a variation of a normalized parameter as a functionof the frequency of sound when two point sources of an acoustic outputapparatus are distributed on both sides of the auricle according to someembodiments of the present disclosure. As shown in FIG. 17 , when thefrequency is less than 10000 Hz, the normalized parameters when thetwo-point sound sources are distributed on both sides of the auricle maybe less than the normalized parameter in the case of mode 1 (no bafflestructure between the two-point sound source, and the distance is D1),mode 2 (no baffle structure between the two-point sound source, and thedistance is D2), and the single-point sound source, which may show thatwhen the two-point sound sources are located on both sides of theauricle, the acoustic output apparatus may have a better capability toreduce the sound leakage.

In order to further explain the effect of the acoustic output apparatuswith or without a baffle between the two point sources or two soundguiding holes, the volume of the near-field sound at the listeningposition and/or volume of the far-field leakage under differentconditions may specifically be described below.

FIG. 18 is a graph illustrating a variation of the volume of a soundheard by the user and volume of a leaked sound as a function of thefrequency of sound with and without a baffle between two point sourcesaccording to some embodiments of the present disclosure. As shown inFIG. 18 , after adding a baffle between the two points of sound sources(i.e., two sound guiding holes) of the acoustic output apparatus, at thenear-field, it may be equivalent to increasing the distance between thetwo points of sound sources, and the sound volume in the near-fieldlistening position may be equivalent to being generated by a set oftwo-point sound sources with a large distance. The near-field soundvolume may significantly be increased compared to the case without abaffle. In the far-field, because the interference of the sound wavesgenerated by the two points of sound sources may be little affected bythe baffle, the sound leakage may be equivalent to being generated by aset of two-point sound sources with a small distance, therefore thesound leakage may not change significantly with or without the baffle.It may be seen that by setting a baffle between two sound guiding holes(i.e., two point sources), the ability of the sound output apparatus toreduce the sound leakage may be effectively improved, and the volume ofthe near-field sound of the acoustic output apparatus may be increasedsignificantly. Therefore, the requirements for sound productioncomponents of the acoustic output apparatus may be reduced. At the sametime, the simple circuit structure may reduce the electrical loss of theacoustic output apparatus, so the working time of the acoustic outputapparatus may be greatly prolonged under a certain amount ofelectricity.

FIG. 19 a graph illustrating a variation of the volume of a sound heardby the user and the volume of a leaked sound as a function of thedistance between two point sources when the frequency of the two pointsources is 300 Hz according to some embodiments of the presentdisclosure. FIG. 20 is a graph illustrating a variation of the volume ofa sound heard by the user and the volume of a leaked sound as a functionof the distance between two point sources when the frequency of the twopoint sources is 1000 Hz according to some embodiments of the presentdisclosure. As shown in FIGS. 19 and 20 , in the near-field, when thefrequency is 300 Hz or 1000 Hz, as the increase of the distance d of thetwo point sources, the volume of the sound heard by the user with abaffle between the two point sources may be greater than that without abaffle between the two point sources, which shows that at thisfrequency, the baffle structure between the two point sources mayeffectively increase the volume of the sound heard by the user in thenear-field. In the far-field, the volume of the leaked sound with abaffle between the two point sources may be equivalent to that without abaffle between the two point sources, which shows that at thisfrequency, with or without a baffle structure arranged between the twopoint sources has little effect on the far-field sound leakage.

FIG. 21 is a graph illustrating a variation of the volume of a soundheard by the user and the volume of a leaked sound as a function of thedistance when the frequency of the two point sources is 5000 Hzaccording to some embodiments of the present disclosure. As shown inFIG. 21 , in the near-field, when the frequency is 5000 Hz, as thedistance d of the two-point sound sources increases, the volume of thesound heard by the user when there is a baffle between the two-pointsound sources may be greater than that when there is no baffle. In thefar-field, the volume of the leaked sound of the two-point sound sourceswith and without baffle may be fluctuant as a function of the distanced. Overall, whether the baffle structure is arranged between thetwo-point sound sources has little effect on the far-field leakage.

FIG. 22 is a graph illustrating a variation of the volume of the heardsound as a function of the frequency when the distance d of thetwo-point sound sources is 1 cm according to some embodiments of thepresent disclosure. FIG. 23 is a graph illustrating a variation of thevolume of the heard sound as a function of the frequency when thedistance d of the two-point sound sources is 2 cm according to someembodiments of the present disclosure. FIG. 24 is a graph illustrating avariation of a normalized parameter of a far-field as a function of thefrequency of sound when the distance d of two point sources is 1 cmaccording to some embodiments of the present disclosure. FIG. 25 is agraph illustrating a variation of a normalized parameter of a far-fieldas a function of the frequency of sound when the distance d of two pointsources is 2 cm according to some embodiments of the present disclosure.FIG. 26 is a graph illustrating a variation of a normalized parameter ofa far-field as a function of the frequency of sound when the distance dof two point sources is 4 cm according to some embodiments of thepresent disclosure. FIG. 27 is a graph illustrating a variation of anormalized parameter of the far-field as a function of the frequency ofsound when the distance d of the two-point sound sources is 4 cmaccording to some embodiments of the present disclosure. As shown inFIGS. 22 through 26 , for the different distance d of the sound guidingholes (for example, 1 cm, 2 cm, 4 cm), at a certain frequency, in thenear-field listening position (for example, the user's ear), the soundvolume that the two sound guiding holes are provided on both sides ofthe auricle (i.e., the “baffle effect” situation shown in the figure),respectively, may be greater than the sound volume that the two soundguiding holes are not provided on both sides of the auricle (i.e., thecase of “no baffle effect” shown in the figure). The certain frequencymay be below 10000 Hz, below 5000 Hz, or below 1000 Hz.

As shown in FIGS. 25 to 27 , for the different distances d of the soundguiding holes (for example, 1 cm, 2 cm, and 4 cm), at a certainfrequency, in the far-field position (for example, the environmentposition away from the user's ear), the volume of the leaked soundgenerated when the two sound guiding holes are provided on both sides ofthe auricle may be smaller than that generated when the two soundguiding holes are not provided on both sides of the auricle. It shouldbe noted that as the distance between two sound guiding holes or twopoint sources increases, the destructive interference of sound at thefar-field position may weaken, leading to a gradual increase in thefar-field leakage and a weaker ability to reduce sound leakage.Therefore, the distance d between two sound guiding holes or the twopoint sources may not be too large. In some embodiments, in order tokeep the output sound as loud as possible in the near-field, andsuppress the sound leakage in the far-field, the distance d between thetwo sound guiding holes may be set to be no more than, for example, 20cm, 12 cm, 10 cm, 6 cm, or the like. In some embodiments, consideringthe size of the acoustic output apparatus and the structuralrequirements of the sound guiding holes, the distance d between the twosound guiding holes may be set to be in a range of, for example, 1 cm to12 cm, 1 cm to 10 cm, 1 cm to 8 cm, 1 cm to 6 cm, 1 cm to 3 cm, or thelike.

It should be noted that the above description is merely for theconvenience of description, and not intended to limit the scope of thepresent disclosure. It may be understood that, for those skilled in theart, after understanding the principle of the present disclosure,various modifications and changes in the forms and details of theacoustic output apparatus may be made without departing from thisprinciple. For example, in some embodiments, a plurality of soundguiding holes may be set on both sides of the baffle. The number ofsound guiding holes on both sides of the baffle may be the same ordifferent. For example, the number of sound guiding holes on one side ofthe baffle may be two, and the number of sound guiding holes on theother side may be two or three. These modifications and changes maystill be within the protection scope of the present disclosure.

In some embodiments, on the premise of maintaining the distance betweenthe two-point sound sources, a relative position of the listeningposition to the two-point sound sources may have a certain effect on thenear-field sound volume and the far-field leakage reduction. In order toimprove the acoustic output effect of the acoustic output apparatus, insome embodiments, the acoustic output apparatus may be provided with atleast two sound guiding holes. The at least two sound guiding holes mayinclude two sound guiding holes located on the front and back sides ofthe user's auricle, respectively. In some embodiments, considering thatthe sound propagated from the sound guiding hole located on the rearside of the user's auricle needs to bypass over the auricle to reach theuser's ear canal, the acoustic route between the sound guiding holelocated on the front side of the auricle and the user's ear canal (i.e.,the acoustic distance from the sound guiding hole to the user's earcanal entrance) is shorter than the acoustic route between the soundguiding hole located on the rear side of the auricle and the user's ear.In order to further explain the effect of the listening position on theacoustic output effect, four representative listening positions(listening position 1, listening position 2, listening position 3,listening position 4) may be selected as shown in FIG. 28 . The effectsand criteria of the selection of the listening position may beexplained. The listening position 1, the listening position 2, and thelistening position 3 may be equal to the distance from the point soundsource a1, which may be r1. The distance between the listening position4 and the point sound source a1 may be r2, and r2<r1. The point soundsource a1 and the point sound source a2 may generate sounds withopposite phases, respectively.

FIG. 29 is a graph illustrating the volume of a sound heard by a user oftwo point sources without baffle at different listening positions as afunction of the frequency of sound according to some embodiments of thepresent disclosure. FIG. 30 is a graph illustrating a normalizedparameter of different listening positions as a function of thefrequency of sound. The normalized parameters may be obtained withreference to Equation (4) based on FIG. 29 , as a function of frequency.As shown in FIGS. 29 and 30 , for the listening position 1, since thedifference between the acoustic routes from the point source a1 and thepoint source a2 to the listening position 1 is small, the difference inamplitude of the sounds produced by the two point sources at thelistening position 1 may be small. Therefore, an interference of thesounds of the two point sources at the listening position 1 may causethe volume of the sound heard by the user to be smaller than that ofother listening positions. For the listening position 2, compared withthe listening position 1, the distance between the listening position 2and the point source a1 may remain unchanged, that is, the acousticroute from the point source a1 to the listening position 2 may notchange. However, the distance between the listening position 2 and thepoint source a2 may be longer, and the length of the acoustic routebetween the point source a2 and the listening position 2 may increase.The amplitude difference between the sound generated by the point sourcea1 and the sound generated by the point source a2 at the listeningposition 2 may increase. Therefore, the volume of the sound transmittedfrom the two point sources after interference at the listening position2 may be greater than that at the listening position 1. Among allpositions on an arc with a radius of r1, a difference between theacoustic route from the point source a1 to the listening position 3 andthe acoustic route from the point source a2 to the listening position 3may be the longest. Therefore, compared with the listening position 1and the listening position 2, the listening position 3 may have thehighest volume of the sound heard by the user. For the listeningposition 4, the distance between the listening position 4 and the pointsource a1 may be short. The sound amplitude of the point source a1 atthe listening position 4 may be large. Therefore, the volume of thesound heard by the user at the listening position 4 may be large. Insummary, the volume of the sound heard by the user at the near-fieldlistening position may change as the listening position and the relativeposition of the two point sources change. When the listening position ison the line between the two point sources and on the same side of thetwo point sources (for example, listening position 3), the acousticroute difference between the two point sources at the listening positionmay be the largest (the acoustic route difference may be the distance dbetween the two point sources). In this case (i.e., when the auricle isnot used as a baffle), the volume of the sound heard by the user at thislistening position may be greater than that at other locations.According to Equation (4), when the far-field leakage is constant, thenormalization parameter corresponding to this listening position may bethe smallest, and the leakage reduction capability may be the strongest.At the same time, reducing the distance r1 between the listeningposition (for example, listening position 4) and the point source a1 mayfurther increase the volume at the listening position, reduce the soundleakage, and improve the capability to reduce leakage.

FIG. 31 is a graph illustrating the volume of the sound heard by theuser of two-point sound sources with baffle (as shown in FIG. 28 ) atdifferent listening positions in the near-field as a function offrequency according to some embodiments of the present disclosure. FIG.32 is a graph of the normalization parameters of different listeningpositions obtained with reference to Equation (4) based on FIG. 31 , asa function of frequency. As shown in FIGS. 31 and 32 , compared to thecase without a baffle, the volume of the sound heard by the user andgenerated by the two point sources at listening position 1 may increasesignificantly when there is a baffle. The volume of the sound heard bythe user at the listening position 1 may exceed that at the listeningposition 2 and the listening position 3. The reason may be that theacoustic route from the point source a2 to the listening position 1 mayincrease after a baffle is set between the two point sources. As aresult, the acoustic route difference between the two point sources atthe listening position 1 may increase significantly. The amplitudedifference between the sounds generated by the two point sources at thelistening position 1 may increase, making it difficult to produce sounddestructive interference, thereby increasing the volume of the soundheard by the user generated at the listening position 1 significantly.At the listening position 4, since the distance between the listeningposition and the point source a1 is further reduced, the sound amplitudeof the point source a1 at this position may be larger. The volume of thesound heard by the user at the listening position 4 may still be thelargest among the four listening positions. For listening position 2 andlistening position 3, since the effect of the baffle on the acousticroute from the point source a2 to the two listening positions is notvery obvious, the volume increase effect at the listening position 2 andthe listening position 3 may be less than that at the listening position1 and the listening position 4 which are closer to the baffle.

The volume of the leaked sound in the far-field may not change withlistening positions, and the volume of the sound heard by the user atthe listening position in the near-field may change with listeningpositions. In this case, according to Equation (4), the normalizationparameter of the acoustic output apparatus may vary in differentlistening positions. Specifically, a listening position with a largevolume of sound heard by the user (e.g., listening position 1 andlistening position 4) may have a small normalization parameter andstrong capability to reduce sound leakage. A listening position with alow volume of sound heard by the user (e.g., listening position 2 andlistening position 3) may have a large normalization parameter and weakcapability to reduce leakage.

Therefore, according to the actual application scenario of the acousticoutput apparatus, the user's auricle may serve as a baffle. In thiscase, the two sound guiding holes on the acoustic output apparatus maybe arranged on the front side and the back side of the auricle,respectively, and the ear canal may be located between the two soundguiding holes as a listening position. In some embodiments, by designingthe positions of the two sound guiding holes on the acoustic outputapparatus, the distance between the sound guiding hole on the front sideof the auricle and the ear canal may be smaller than the distancebetween the sound guiding hole on the back side of the auricle and theear canal. In this case, because the sound guiding hole on the frontside of the auricle is close to the ear canal, it may produce a largesound amplitude at the ear canal. The sound amplitude produced by thesound guiding hole on the back of the auricle may be smaller at the earcanal, which may avoid the destructive interference of the sound at thetwo sound guiding holes at the ear canal, thereby ensuring that thevolume of the sound heard by the user at the ear canal is large. In someembodiments, the acoustic output apparatus may include a contactpoint(s) that can contact with the auricle when worn (e.g., “aninflection point” on a supporting structure to match the shape of theear). The contact point(s) may be located on a line connecting the twosound guiding holes or on one side of the line connecting the two soundguiding holes. And a ratio of the distance between the front soundguiding hole and the contact point(s) to the distance between the rearsound guiding hole and the contact point(s) may be 0.05-20. Preferably,the ratio may be 0.1-10. More preferably, the ratio may be 0.2-5. Evenmore preferably, the ratio may be 0.4-2.5.

FIG. 33 is a schematic diagram illustrating two-point sound sources anda baffle (e.g., an auricle) according to some embodiments of the presentdisclosure. In some embodiments, a position of the baffle between thetwo sound guiding holes may also have a certain influence on the soundoutput effect. Merely by way of example, as shown in FIG. 33 , a bafflemay be provided between a point sound source a1 and a point sound sourcea2, a listening position may be located on the line connecting the pointsound source a1 and the point sound source a2. In addition, thelistening position may be located between the point sound source a1 andthe baffle. A distance between the point sound source a1 and the bafflemay be L. A distance between the point sound source a1 and the pointsound source a2 may be d. A distance between the point sound source a1and the sound heard by the user may be L1. A distance between thelistening position and the baffle may be L2. When the distance L1 isconstant, a movement of the baffle may cause different ratios of L to d,thereby achieving a volume of the sound heard by the user at thelistening position and/or the far-field leakage volume under thedifferent ratios.

FIG. 34 is a graph illustrating a variation of the volume of anear-field sound as a function of the frequency of sound when a baffleis at different positions according to some embodiments of the presentdisclosure. FIG. 35 is a graph illustrating a variation of the volume ofa far-field leakage as a function of the frequency of sound when abaffle is at different positions according to some embodiments of thepresent disclosure. FIG. 36 is a graph illustrating a variation of anormalization parameter as a function of the frequency of sound when abaffle is at different positions according to some embodiments of thepresent disclosure. According to FIGS. 34-36 , the volume of thefar-field leakage may vary little with the change of the position of thebaffle between the two point sources. In a situation that the distance dbetween the point source a1 and the point source a2 remains constant,when L decreases, the volume at the listening position may increase, thenormalization parameter may decrease, and the ability to reduce leakagemay be enhanced. In the same situation, when L increases, the volume atthe listening position may increase, the normalization parameter mayincrease, and the ability to reduce leakage may be weakened. A reasonfor the above result may be that when L is small, the listening positionmay be close to the baffle, an acoustic route of the sound wave from thepoint source a2 to the listening position may be increased due to thebaffle. In this case, an acoustic route difference between the pointsource a1 and the point source a2 to the listening position may beincreased and the destructive interference of the sound may be reduced.As a result, the volume at the listening position may be increased afterthe baffle is added. When L is large, the listening position may be faraway from the baffle. The baffle may have a small effect on the acousticroute difference between the point source a1 and the point source a2 tothe listening position. As a result, a volume change at the listeningposition may be small after the baffle is added.

As described above, by designing positions of the sound guiding holes onthe acoustic output apparatus, an auricle of a human body may serve as abaffle to separate different sound guiding holes when the user wears theacoustic output apparatus. In this case, a structure of the acousticoutput apparatus may be simplified, and an output effect of the acousticoutput apparatus may be further improved. In some embodiments, thepositions of the two sound guiding holes may be designed so that a ratioof a distance between the sound guiding hole on the front side of theauricle and the auricle (or a contact point on the acoustic outputapparatus for contact with the auricle) to a distance between the twosound guiding holes may be less than or equal to 0.5 when the user wearsthe acoustic output apparatus. Preferably, the ratio may be less than orequal to 0.3. More preferably, the ratio may be less than or equal to0.1. In some embodiments, the ratio of the distance between the soundguiding hole on the front side of the auricle and the auricle (or acontact point on the acoustic output apparatus for contact with theauricle) to the distance between the two sound guiding holes may belarger than or equal to 0.05. In some embodiments, a second ratio of thedistance between the two sound guiding holes to the height of theauricle may be larger than or equal to 0.2. In some embodiments, thesecond ratio may be less than or equal to 4. In some embodiments, theheight of the auricle may refer to a length of the auricle in adirection perpendicular to a sagittal plane.

It should be noted that an acoustic route from an acoustic driver to asound guiding hole in the acoustic output apparatus may have a certaineffect on the volumes of the near-field sound and far-field soundleakage. The acoustic route may be changed by adjusting a cavity lengthbetween a vibration diaphragm in the acoustic output apparatus and thesound guiding hole. In some embodiments, the acoustic driver may includea vibration diaphragm. The front and rear sides of the vibrationdiaphragm may be coupled to two sound guiding holes through a frontchamber and a rear chamber, respectively. The acoustic routes from thevibration diaphragm to the two sound guiding holes may be different. Insome embodiments, a ratio of the lengths of the acoustic routes betweenthe vibration diaphragm and the two sound guiding holes may be, forexample, 0.5-2, 0.6-1.5, or 0.8-1.2.

In some embodiments, on the premise of keeping the phases of the soundsgenerated at the two sound guiding holes opposite, the amplitudes of thesounds generated at the two sound guiding holes may be changed toimprove the output effect of the acoustic output apparatus.Specifically, impedances of acoustic routes connecting the acousticdriver and the two sound guiding holes may be adjusted so as to adjustthe sound amplitude at each of the two sound guiding holes. In someembodiments, the impedance may refer to a resistance that a medium needsto overcome during displacement when acoustic waves are transmitted. Theacoustic routes may or may not be filled with a damping material (e.g.,a tuning net, a tuning cotton, etc.) so as to adjust the soundamplitude. For example, a resonance cavity, a sound hole, a sound slit,a tuning net, and/or a tuning cotton may be disposed in an acousticroute so as to adjust the acoustic resistance, thereby changing theimpedances of the acoustic route. As another example, an aperture ofeach of the two sound guiding holes may be adjusted to change theacoustic resistance of the acoustic routes corresponding to the twosound guiding holes. In some embodiments, a ratio of the acousticimpedance of the acoustic route between the acoustic driver (thevibration diaphragm) and one of the two sound guiding holes to theacoustic route between the acoustic driver and the other sound guidinghole may be 0.5-2 or 0.8-1.2.

It should be noted that the above description is only for theconvenience of description, and is not intended to limit the presentdisclosure. It should be understood that, for those skilled in the art,after understanding the principle of the present disclosure, they maymake various modifications and changes in the forms and details of theacoustic output apparatus without departing from violating thisprinciple. For example, the listening position may not be on the lineconnecting the two-point sound source, but may also be above, below, orin an extension direction of the line connecting the two-point soundsources. As another example, a measurement method of the distance from apoint sound source to the auricle, and a measurement method of theheight of the auricle may also be adjusted according to differentscenarios. These similar changes may be all within the protection scopeof the present disclosure.

FIG. 37 is a schematic diagram illustrating another exemplary acousticoutput apparatus according to some embodiments of the presentdisclosure.

For human ears, the frequency band of sound that can be heard may beconcentrated in a mid-low-frequency band. An optimization goal in themid-low-frequency band may be to increase a volume of the sound heard bythe user. If the listening position is fixed, parameters of the twopoint sources may be adjusted such that the volume of the sound heard bythe user may increase significantly while a volume of leaked sound maybe substantially unchanged (an increase in the volume of the sound heardby the user may be greater than an increase in the volume of the soundleakage). In a high-frequency band, a sound leakage reduction effect ofthe two-point sound sources may be weaker. In the high-frequency band,an optimization goal may be to reduce sound leakage. The sound leakagemay be further reduced and a leakage-reducing frequency band may beexpanded by adjusting the parameters of the two-point sound sources ofdifferent frequencies. In some embodiments, the acoustic outputapparatus 1000 may also include an acoustic driver 1030. The acousticdriver 1030 may output sound from two of second sound guiding holes.Details regarding the acoustic driver 1030, the second sound guidingholes, and a structure therebetween may be described with reference tothe acoustic driver 1020 and the first sound guiding holes. In someembodiments, the acoustic driver 1030 and the acoustic driver 1020 mayoutput sounds of different frequencies, respectively. In someembodiments, the acoustic output apparatus may further include acontroller configured to cause the acoustic driver 1020 to output soundin the first frequency range, and to cause the acoustic driver 1030 tooutput sound in the second frequency range, wherein the second frequencyrange may include frequencies higher than the first frequency range. Forexample, the first frequency range may be 100 Hz-1000 Hz, and the secondfrequency range may be 1000 Hz-10000 Hz.

In some embodiments, the acoustic driver 1020 may be a low-frequencyspeaker, and the acoustic driver 1030 may be a mid-high-frequencyspeaker. Due to different frequency response characteristics of thelow-frequency speaker and the mid-high-frequency speaker, frequencybands of the output sound may also be different. High-frequency bandsand low-frequency bands may be divided by using the low-frequencyspeakers and the mid-high-frequency speakers, and accordingly,low-frequency tow-point sound sources and mid-high-frequency two-pointsound sources may be constructed to perform near-field sound output anda far-field leakage reduction. For example, the acoustic driver 1020 mayprovide two-point sound sources for outputting low-frequency soundthrough the sound guiding hole 1011 and the sound guiding hole 1012,which may be mainly used for outputting sound in low-frequency bands.The low-frequency two-point sound sources may be distributed on bothsides of an auricle to increase a volume near the near-field ear. Theacoustic driver 1030 may provide two-point sound sources for outputtingmid-high-frequency bands through two of the second sound guiding holes.A mid-high-frequency sound leakage may be reduced by adjusting adistance between the two second sound guiding holes. Themid-high-frequency two-point sound sources may be distributed on bothsides of the auricle or on the same side of the auricle. Alternatively,the acoustic driver 1020 may provide two-point sound sources foroutputting full-frequency sound through the sound guiding hole 1011 andthe sound guiding hole 1012 so as to further increase the volume of thenear-field sound.

Further, a distance d2 between the two second sound guiding holes may beless than a distance d1 between the sound guiding hole 1011 and thesound guiding holes 1012, that is, d1 may be larger than d2. Forillustration purpose, as shown in FIG. 9 , it may be possible to obtainstronger sound leakage reduction capabilities than a single-point soundsource and one set of two-point sound sources by setting two sets oftwo-point sound sources including one set of low-frequency two-pointsound sources and one set of high-frequency two-point sound sources withdifferent distances.

It should be noted that the position of the sound guiding holes of theacoustic output apparatus may be not limited to the case that the twosound guiding holes 1011 and 1012 corresponding to the acoustic driver1020 shown in FIG. 37 are distributed on both sides of the auricle, andthe case that the two sound guiding holes corresponding to the acousticdriver 1030 are distributed on the front side of the auricle. Forexample, in some embodiments, two second sound guiding holescorresponding to the acoustic driver 1030 may be distributed on the sameside of the auricle (e.g., a rear side, an upper side, or a lower sideof the auricle). As another example, in some embodiments, the two secondsound guiding holes corresponding to the acoustic driver 1030 may bedistributed on both sides of the auricle. In some embodiments, when thesound guiding holes 1011 and the sound guiding hole 1012 (and/or the twosecond sound guiding holes) are located on the same side of the auricle,a baffle may be disposed between the sound guiding holes 1011 and thesound guiding hole 1012 (and/or the two second sound guiding holes) soas to further increase the near-field sound volume and reduce thefar-field sound leakage. For a further example, in some embodiments, thetwo sound guiding holes corresponding to the acoustic driver 1020 mayalso be located on the same side of the auricle (e.g., a front side, arear side, an upper side, or a lower side of the auricle).

In practical applications, the acoustic output apparatus may includedifferent product forms such as bracelets, glasses, helmets, watches,clothing, or backpacks, smart headsets, etc. In some embodiments, anaugmented reality technology and/or a virtual reality technology may beapplied in the acoustic output apparatus so as to enhance a user's audioexperience. For illustration purposes, a glass with a sound outputfunction may be provided as an example. Exemplary glasses may be orinclude augmented Reality (AR) glasses, virtual reality (VR) glasses,etc.

FIG. 38 is a schematic diagram illustrating an exemplary noise reductionsystem 3800 according to some embodiments of the present disclosure. Thenoise reduction system 3800 may be used to reduce or eliminate noise(e.g., an unwanted sound that is unpleasant, loud, or disruptive tohearing). For example, the noise may include a background sound, such astraffic noise, wind noise, water noise, foreign speech. The noisereduction device 3800 may be applied in various areas and/or devices,such as a headphone (e.g., a noise-canceling headphone, a boneconduction headphone), a smart device (e.g., a smart glass like an AR/VRglass), a muffler, an anti-snoring device, or the like, or anycombination thereof. The AR/VR glass may include a frame and lenses. TheAR/VR glass may be provided with a plurality of components which mayimplement different functions. Details regarding structures andcomponents of the AR/VR glass may be described with reference to theglass 100 illustrated in FIG. 48 . In some embodiments, the noisereduction device 3800 may be an active noise reduction device thatreduces a noise by generating a noise reduction signal designed toreduce the noise (e.g., a signal that has an inverted phase to thenoise). In some embodiments, the noise reduction system 3800 may be apassive noise reduction system that reduces noise by differentiatingsound signals collected by two microphone arrays at different positions.

As shown in FIG. 38 , the noise reduction system 3800 may include anaudio sensor 3810, a noise reduction device 3820, and a combinationdevice 3830. As used herein, a connection between two components of thenoise reduction system 3800 may include a wireless connection, a wiredconnection, any other communication connection that can enable datatransmission and/or reception, and/or any combination of theseconnections. The wireless connection may include, for example, aBluetooth™ link, a Wi-Fi™ link, a WiMax™ link, a WLAN link, a ZigBeelink, a mobile network link (e.g., 3G, 4G, 5G, etc.), or the like, or acombination thereof. The wired connection may include, for example, acoaxial cable, a communication cable (e.g., a telecommunication cable),a flexible cable, a spiral cable, a non-metallic sheath cable, a metalsheath cable, a multi-core cable, a twisted-pair cable, a ribbon cable,a shielded cable, a double-strand cable, an optical fiber, an electricalcable, an optical cable, a telephone wire, or the like, or anycombination thereof.

The audio sensor 3810 may detect a sound from the user, a smart device4240, and/or ambient environment, and generate a plurality of sub-bandsound signals in response to the detected sound. In some embodiments,the one or more microphones or microphone arrays may be genericmicrophones. In some embodiments, the one or more microphones or themicrophone array may be customized to the augmented reality or thevirtual reality. The audio sensor 3810 may include one or moremicrophones or a microphone array. In some embodiments, the audio sensor3810 may include one or more low-frequency microphones and one or morehigh-frequency microphones. The low-frequency microphones may be used tocollect a low-frequency sound signal. The high-frequency microphones maybe used to collect a high-frequency sound signal. In some embodiments,the low-frequency microphone and the high-frequency microphone may beintegrated into a single component. For example, the low-frequencymicrophones and/or the high-frequency microphones may be integrated intoa centralized microphone array in the form of a straight line or a ring.In some embodiments, the low-frequency microphones and/or thehigh-frequency microphones may be distributedly arranged in a device(e.g., the AR/VR glass) to form a distributed microphone array. Forexample, the low-frequency microphones and/or the high-frequencymicrophones may be disposed at various positions of the device, and themicrophones may be wirelessly connected.

In some embodiments, each microphone in the audio sensor 3810 may beused to detect a sound (which may include both desired sound and anoise) and generate one or more sub-band voice signals. In someembodiments, each microphone in the microphone array 3810 may beconnected to a filter, which is configured to generate the one or moresub-band sound signals by processing the detected sound. A sound signalmay have a specific frequency band. A sub-band sound signal refers to asignal having a frequency band narrower than and within the frequencyband of the sound signal. For example, the sound signal may have afrequency band ranging from 10 Hz to 30 kHz. The frequency band of asub-band noise signal may be 100-200 HZ, which is within the frequencyband of the sound signal. In some embodiments, a combination of thefrequency bands of the sub-band noise signals may cover the frequencyband of the sound. Additionally or alternatively, at least two of thesub-band sound signals may have different frequency bands. Optionally,each of the sub-band sound signals may have a distinctive frequency banddifferent from the frequency band(s) of the other sub-band soundsignal(s). Different sub-band sound signals may have the same frequencybandwidth or different frequency bandwidths. In some embodiments, anoverlap between the frequency bands of a pair of adjacent sub-band soundsignals in the frequency domain may be avoided, so as to improve thenoise reduction effect. As used herein, two sub-band sound signal whosecenter frequencies are adjacent to each other among the sub-band soundsignals may be regarded as being adjacent to each other in the frequencydomain. More descriptions regarding the frequency bands of a pair ofadjacent sub-band sound signals may be found elsewhere in the presentdisclosure. See, e.g., FIGS. 40A and 40B and relevant descriptionsthereof.

In some embodiments, the sub-band noise signals generated by the audiosensor 3810 may be digital signals or analog signals. In someembodiments, each microphone in the audio sensor 3810 may be a MicroElectro Mechanical System (MEMS) microphone. The MEMS microphone mayhave a low operating current, stable performance, and high voicequality. In some embodiments, all or a portion of the microphones in theaudio sensor 3810 may be other types of microphones, which is notlimited herein.

The noise reduction device 3820 may be configured to reduce or eliminatethe noise in the sub-band sound signals generated by the audio sensor3810. In some embodiments, the noise reduction device 3820 may performnoise estimation, adaptive filtering, audio enhancement, and the like,on the sub-band sound signals, thereby realizing noise reduction in thesub-band sound signals. For each of the sub-band sound signals, thenoise reduction device 3820 may determine a sub-band noise signalaccording to a noise estimation algorithm, and generate a sub-band noisecorrection signal according to the sub-band noise signal. For example,the sub-band noise correction signal may be an analog signal or adigital signal having an inverted phase to the sub-band noise signal. Insome embodiments, the noise estimation algorithm may include atime-recursive average noise estimation algorithm, a minimum trackingnoise estimation algorithm, or the like, or a combination thereof. Thenoise reduction device 3820 may further generate a target sub-band voicesignal based on the sub-band voice signal and the sub-band noisecorrection signal, thereby reducing the noise in the correspondingsub-band sound signals. In some embodiments, the audio sensor 3810 mayinclude at least one pair of low-frequency microphones and at least onepair of high-frequency microphones. Each pair of the microphones maygenerate a sub-band sound signal within a frequency band of thecorresponding pair of the microphones. For illustration, a pair ofmicrophones including a first microphone closer to a main sound source(e.g., the mouth of a user) and a second microphone farther away fromthe main sound source is taken as an example to describe the noisereduction of noise reduction device 3820. The noise reduction device3820 may take a sound signal generated by the first microphone as asub-band sound signal, and another sound signal generated by the secondmicrophone as a sub-band noise signal. The noise reduction device 3820may further reduce the noise in the sub-band sound signal and generatethe target sub-band voice signal by differentiating the sub-band soundsignal and the sub-band noise signal. More descriptions regarding thenoise reduction device 3820 and the sub-band noise signal may be foundelsewhere in the present disclosure. See, e.g., FIGS. 39A, 41 , and FIG.42 and relevant descriptions thereof.

The combination device 3830 may be configured to combine the targetsub-band voice signal to generate a target signal. The combinationdevice 3830 may include any component that can combine a plurality ofsignals. For example, the combination device 3830 may generate a mixedsignal (i.e., the target signal) according to a signal combinationtechnique, such as a frequency division multiplexing technique.

It should be noted that the above descriptions of the noise reductiondevice 3800 are provided for the purposes of illustration, and notintended to limit the scope of the present disclosure. For personshaving ordinary skills in the art, various modifications and changes inthe forms and details of the application of the above method and systemmay occur without departing from the principles of the presentdisclosure. In some embodiments, the noise reduction system 3800 mayinclude one or more additional components. Additionally oralternatively, one or more components of the noise reduction system 3800described above may be omitted. For example, a residual noise reductiondevice may be added to the noise reduction device 3820. In addition, twoor more components of the noise reduction system 3800 may be integratedinto a single component. Merely by way of example, in the noisereduction system 3800, the combination device 3830 may be integratedinto the noise reduction device 3820.

FIG. 39A is a schematic diagram illustrating an exemplary noisereduction system 3900A according to some embodiments of the presentdisclosure. As shown in FIG. 39A, the noise reduction system 3900A mayinclude a microphone array 3910 a, a noise reduction device 3920 a, anda combination device 3930 a. The microphone array 3910 a may include aplurality of microphones 3912 a, for example, a microphone 3912 a-1, amicrophone 3912 a-2, . . . , a microphone 3912 a-n. The “n” may be anypositive integer greater than 1, such as 5, 10, 15, or the like. Themicrophone array 3910 a may be configured to detect a sound S, andgenerate a plurality of sub-band noise signals (e.g., sub-band soundsignals S1 to Sn). A count (i.e., n) of microphones 3912 a may be equalto a count of sub-band sound signals. The count of sub-band speechsignals (i.e., n) may be related to a frequency band of the sound S anda frequency band of the generated sub-band speech signals. For example,a certain count of microphones 3912 a may be used generate the pluralityof sub-band sound signals, so that a combination of frequency bands ofthe sub-band sound signals may cover the frequency band of the sound S.Optionally, an overlap between the frequency bands of any pair ofadjacent sub-band noise signals in the frequency domain may be avoided,so as to improve the noise reduction effect.

The microphone 3912 a may have different frequency responses and may beconfigured to generate a sub-band sound signal by processing the soundS. For example, the microphone 3912 a-1 may respond to a sound with afrequency of 20 Hz to 3 kHz. Then microphone 3912 a-1 may generate asub-band sound signal with a frequency range of 20 Hz to 3 kHz byprocessing a full-band (for example, 2 Hz to 30 kHz) sound S. In someembodiments, the sub-band sound signal generated by the microphone array3910 a may be a digital signal or an analog signal.

In some embodiments, the microphone 3912 a may include an acousticchannel element and a sound-sensitive component. The acoustic channelcomponent may form a path through which a sound S (e.g., the targetsound signal and the noise mentioned in FIG. 38 ) is transmitted to asound-sensitive component. For example, the acoustic channel componentmay include one or more chamber structures, one or more pipe structures,or the like, or a combination thereof. The sound-sensitive component mayconvert a sound S (for example, the original sound S or processed soundafter passing through the acoustic channel component)) sent from theacoustic channel component into an electric signal. For example, thesound-sensitive component may include a diaphragm, a plate, acantilever, etc. Taking the diagram as an example, the diaphragm may beused to convert a change of sound pressure caused by a sound signal onthe diaphragm surface into a mechanical vibration of the diaphragm. Thesound-sensitive component may be made of one or more materialsincluding, for example, plastic, metal, piezoelectric material, or thelike, or any composite material.

In some embodiments, the frequency response of the microphone 3912 a maybe associated with the acoustic structure of the acoustic channelcomponent of the microphone 3912 a. For example, the acoustic channelcomponent of the microphone 3912 a may have a specific acousticstructure, which may process the sound before it reaches thesound-sensitive component of the microphone 3912 a. In some embodiments,the acoustic structure of the acoustic channel component may have aspecific acoustic impedance, so that the acoustic channel component mayfunction as a filter that filters the sound to generate a sub-bandsound. The sound-sensitive component of the microphone 3912 a may thenconvert the sub-band sound into a sub-band sound electrical signal.

In some embodiments, the acoustic impedance of the acoustic structuremay be set according to the frequency band of the sound. In someembodiments, an acoustic structure mainly including a chamber structuremay function as a high-pass filter, while an acoustic structure mainlyincluding a pipe structure that may function as a low-pass filter.Merely by way of example, the acoustic channel component may have achamber-pipe structure. The chamber-pipe structure may be a combinationof a sound capacity and an acoustic mass in serial, and aninductor-capacitor (LC) resonance circuit may be formed. If an acousticimpedance material is used in the chamber-pipe structure, aresistor-inductor-capacitor (RLC) series loop may be formed, and theacoustic impedance of the RLC series loop may be determined according toEquation (5), as follows:

$\begin{matrix}{{Z = {R_{a} + {j\left( {{\omega M_{a}} - \frac{1}{\omega C_{a}}} \right)}}},} & (5)\end{matrix}$where Z refers to the acoustic impedance of the acoustic channelcomponent, ω refers to an angular frequency of the chamber-pipestructure, j refers to a unit imaginary number, M_(a) refers to theacoustic mass, C_(a) refers to the sound capacity, and R_(a) refers tothe acoustic resistance of the RLC series loop.

The chamber-pipe structure may function as a band-pass filter (denotedas F1). The bandwidth of the band-pass filter F1 may be adjusted byadjusting the acoustic resistance R_(a). The center frequency ω₀ of theband-pass filter F1 may be adjusted by adjusting the acoustic mass M_(a)and/or the sound capacity C_(a). For example, the center frequency ω₀ ofthe band-pass filter F1 may be determined according to Equation (6) asbelow:

$\begin{matrix}{{\omega_{0} = \sqrt{M_{a}C_{a}}}.} & (6)\end{matrix}$

In some embodiments, the frequency response of a microphone 3912 a maybe associated with a physical characteristic (e.g., the material, thestructure) of the sound-sensitive component of the microphone 3912 a.The sound-sensitive component having a specific physical characteristicmay be sensitive to a certain frequency band of the sound. For example,the mechanical vibration of one or more elements in the sound-sensitivecomponent may lead to change(s) in electric parameter(s) of thesound-sensitive component. The sound-sensitive component may besensitive to a certain frequency band of a sound signal. The frequencyband of the sound signal may cause corresponding changes in electricparameters of the sound-sensitive component. In other words, the diagrammay function as a filter that processes a sub-band of the sound S. Insome embodiments, the sound S may be transmitted to the sound-sensitivecomponent through the acoustic channel component without (orsubstantially without) being filtered by the acoustic channel component.The physical characteristic of the sound-sensitive component may beadjusted, such that the sound-sensitive component may function as afilter that filter the sound S and convert the filtered sound into asub-band sound electrical signal.

Merely by way of example, the sound-sensitive component may include adiaphragm, which may function as a band-pass filter (denoted as F2). Thecenter frequency ω′₀ of the band-pass filter F2 may be determinedaccording to Equation (7) as below:

$\begin{matrix}{{\omega_{0}^{\prime} = \sqrt{\frac{K_{m}}{M_{m}}}},} & (7)\end{matrix}$where M_(m) refers to the mass of the diaphragm, and K_(m) refers to theelasticity coefficient of the diaphragm. R_(m) refers to a damping ofthe diaphragm. The bandwidth of the band-pass filter F2 may be adjustedby adjusting R_(m). The center frequency ω′₀ of the band-pass filter F2may be adjusted by adjusting the mass of the diaphragm and/or theelasticity coefficient of the diaphragm.

As described above, the acoustic channel component or thesound-sensitive component of the microphone 3912 a may function as afilter. The frequency response of the acoustic-electric transducer 610may be adjusted by modifying parameter(s) of the acoustic channelcomponent (e.g. R_(a), M_(a), and/or C_(a)) or parameter(s) thesound-sensitive component (e.g. K_(m), and/or R_(m)). In somealternative embodiments, a combination of the acoustic channel componentand the sound-sensitive component may function as a filter. By modifyingparameters of the acoustic channel component and the sound-sensitivecomponent, the frequency response of the combination of the acousticchannel component and the sound-sensitive component may be adjustedaccordingly. More descriptions regarding the acoustic channel componentand/or the sound-sensitive component which function as a band-passfilter may be found in, for example, PCT Application No.PCT/CN2018/105161 filed on Sep. 12, 2018 entitled “SIGNAL PROCESSINGDEVICE HAVING MULTIPLE ACOUSTIC-ELECTRIC TRANSDUCERS,” the contents ofwhich are hereby incorporated by reference.

The sub-band noise reduction device 3920 a may include a sub-band noisereduction unit 3922 a-1, a sub-band noise reduction unit 3922 a-2, . . ., and a sub-band noise reduction unit 3922 a-n as shown in FIG. 39A. Insome embodiments, the count (or number) of the sub-band noise reductionunits 3922 a may be equal to the count (or number) of the sub-band noisesignals generated by the microphones 3912 a. Each of the sub-band noisereduction units 3922 a may be configured to receive one of the sub-bandsound signals from the microphones 3912 a, and generate a sub-band noisecorrection signal for reducing a noise (also referred to as a sub-bandnoise) in the received sub-band sound signal. For example, as shown inFIG. 39A, a sub-band noise reduction module 3922 a-i (i being a positiveinteger equal to or smaller than n) may receive a sub-band sound signalSi from the microphones 3912 a and generate a sub-band noise correctionsignal Ci for reducing the noise in the sub-band sound signal Si. Insome embodiments, the sub-band noise reduction unit 3922 a may include asub-band noise estimation sub-unit (not shown) and a sub-band noisesuppression sub-unit (not shown). The sub-band noise estimation sub-unitmay be configured to estimate noise in a sub-band sound signal. Thesub-band noise suppression sub-unit may be configured to receive thenoise in the sub-band sound signal from the sub-band noise estimationsub-unit, and generate a sub-band noise correction signal to reduce asub-band noise in the sub-band sound signal.

In some embodiments, the sub-band sound signals may be transmitted viaparallel transmitters from the microphones 3912 a to the sub-band noisereduction units 3922 a. Optionally, a sub-band sound signal may betransmitted via a transmitter according to a certain communicationprotocol for transmitting digital signals. Exemplary communicationprotocols may include AES3 (audio engineering society), AES/EBU(European broadcast union)), EBU (European broadcast union), ADAT(Automatic Data Accumulator and Transfer), I2S (Inter-IC Sound), TDM(Time Division Multiplexing), MIDI (Musical Instrument DigitalInterface), CobraNet, Ethernet AVB (Ethernet Audio/VideoBridging),Dante, ITU (International Telecommunication Union)-T G.728, ITU-T G.711,ITU-T G.722, ITU-T G.722.1, ITU-T G.722.1 Annex C, AAC (Advanced AudioCoding)-LD, or the like, or a combination thereof. The digital signalmay be transmitted in a certain format including a CD (Compact Disc),WAVE, AIFF (Audio Interchange File Format), MPEG (Moving Picture ExpertsGroup)-1, MPEG-2, MPEG-3, MPEG-4, MIDI (Musical Instrument DigitalInterface), WMA (Windows Media Audio), RealAudio, VQF (Transform-domainWeighted Nterleave Vector Quantization), AMR (Adaptibve Multi-Rate),APE, FLAC (Free Lossless Audio Codec), AAC (Advanced Audio Coding), orthe like, or a combination thereof. In some alternative embodiments, thesub-band sound signals may be processed to a single-channel signalusing, e.g., a frequency-division multiplexing technique, andtransmitted to the sub-band noise reduction units 3922 a.

In some embodiments, the sub-band noise reduction unit 3922 a-i mayfirst estimate a sub-band noise signal N_(i), and perform a phasemodulation and/or an amplitude modulation on the sub-band noise signalN_(i) to generate the corresponding sub-band noise correction signalN_(i)′. In some embodiments, the phase modulation and the amplitudemodulation may be performed in sequence or simultaneously on thesub-band noise signal N_(i)′. For example, the sub-band noise reductionunit 3922 a-i may first perform a phase modulation on the sub-band noisesignal N_(i) to generate a phase modulated signal, and then perform anamplitude modulation on the phase modulated signal to generate thecorresponding sub-band noise correction signal N_(i)′. The phasemodulation of the sub-band noise signal N_(i) may include an inversionof the phase of the sub-band noise signal N_(i). Optionally, in someembodiments, a phase displacement (or shift) of the sub-band noise mayoccur during its transmission from a location at the microphone 3912 ato a location at the sub-band noise reduction unit 3922 a-i. The phasemodulation of the sub-band noise signal N_(i) may further include acompensation of the phase displacement of the sub-band noise signalN_(i) during signal transmission. Alternatively, the sub-band noisereduction unit 3922 a-i may first perform an amplitude modulation on thesub-band noise signal N_(i) to generate an amplitude modulated signal,and then perform a phase modulation on the amplitude modulated signal togenerate the sub-band noise correction signal More descriptionsregarding the sub-band noise reduction unit 3922 a-i may be foundelsewhere in the present disclosure. See, e.g., FIGS. 41 to 42 andrelevant descriptions thereof.

In some embodiments, the noise reduction device 3920 a may perform noisereduction using two sets of microphones (e.g., two microphone arrays3910 a) having the same configuration according to the dual microphonenoise reduction principle. Each set of microphones may include aplurality of microphones that may generate a plurality of sub-band soundsignals having different frequency bands. For illustration, the two setsof microphones with the same configuration may be referred to as a firstmicrophone set and a second microphone set. The first microphone set maybe closer to a main sound source (e.g., the mouth of a user) than thesecond microphone set. Each first microphone in the first microphonesset may correspond to one second microphones in the second microphoneset. For example, a first microphone having a frequency band of 20 Hz to3 kHz may correspond to a second microphone having a frequency band of20 Hz to 3 kHz. A signal generated by the first microphone may be usedas a sub-band sound signal, and a signal generated by the secondmicrophone may be used as a sub-band noise signal. The noise reductiondevice 3920 a may generate a target sub-band sound signal based on thesub-band voice signal and the sub-band noise signal. More descriptionsregarding the noise reduction using two microphone arrays may be foundelsewhere in the present disclosure. See, e.g., FIG. 46 and relevantdescriptions thereof.

The combination device 3930 a may be configured to combine the targetsub-band sound signals to generate a target signal S′.

FIG. 39A is a schematic diagram illustrating another exemplary noisereduction system 3900B according to some embodiments of the presentdisclosure. The noise reduction device 3900B may be similar to the noisereduction device 3900A, except for certain components or features. Asshown in FIG. 39B, the noise reduction system 3900B may include amicrophone array 3910 b, a noise reduction device 3920 b, and acombination device 3930 b. The microphone array 3910 b may include aplurality of microphones 3912 b and a plurality of filters 3914 b. Acount of microphones 3912 b, a count of filters 3914 b, and a count ofsub-band voice signals may be equal. The microphones 3912 b may have thesame configuration. In other words, each microphone 3912 b may have thesame frequency response. Each microphone 3912 b may be coupled to afilter 3914 b. The filter 3914 b may have different frequency responsesto the sound S. The microphone array 3910 b may detect the sound S bythe microphones 3912 b, and generate a plurality of sub-band soundsignals by the corresponding filter 3914 b in response to the detectedsound S. Exemplary filters 3914 b may include passive filters, activefilters, analog filters, digital filters, or the like, or a combinationthereof.

The noise reduction device 3920 b may include a plurality of sub-bandnoise reduction units 3922 b. Each sub-band noise reduction unit 3922 bmay be coupled to a filter 3914 b (or a microphone 3912 b). The noisereduction device 3920 b may have the same configuration and function asthat of the noise reduction device 3920 a, and the combination device3930 b may have the same configuration and function as that of thecombination device 3930 a. More descriptions regarding the noisereduction device 3920 b and the combination device 3930 b may be foundelsewhere in the present disclosure. See, e.g., FIG. 39A and relevantdescriptions thereof.

It should be noted that the above descriptions of the noise reductiondevice 3900A and 3900B are provided for the purposes of illustration,and not intended to limit the scope of the present disclosure. Forpersons having ordinary skills in the art, various modifications andchanges in the forms and details of the application of the above methodand system may occur without departing from the principles of thepresent disclosure. In some embodiments, the noise reduction system3900A and/or 3900B may include one or more additional components.Additionally or alternatively, one or more components of the noisereduction system 3900A and/or 3900B described above may be omitted. Inaddition, two or more components of the noise reduction system 3800Aand/or 3900B may be integrated into a single component.

FIG. 40A illustrates an exemplary frequency response 4010 of a thirdmicrophone and an exemplary frequency response 4020 of a fourthmicrophone according to some embodiments of the present disclosure. FIG.40B illustrates the frequency response 4010 of the third microphone andanother exemplary frequency response 4030 of the fourth microphoneaccording to some embodiments of the present disclosure. The thirdmicrophone may be configured to process a sound to generate a firstsub-band sound signal. The fourth microphone may be configured toprocess a sound to generate a second sub-band sound signal. The secondsub-band sound signal may be adjacent to the first sub-band sound signalin the frequency domain.

In some embodiments, the frequency responses of the third and fourthmicrophone s may have the same frequency bandwidth. For example, asshown in FIG. 40A, the frequency response 4010 of the third microphonehas a lower half-power point f₁, an upper half-power point f₂, and acenter frequency f₃. As used herein, a half power point of a certainfrequency response may refer to a frequency point with a specificattenuation of power level (e.g., −3 Db). The frequency bandwidth of thefrequency response 4010 may be equal to a difference between f₂ and f₁.The frequency response 4020 of the fourth microphone has a lowerhalf-power point f₂, an upper half-power point f₄, and a centerfrequency f₅. The frequency bandwidth of the frequency response 4020 maybe equal to a difference between f₄ and f₂. The frequency bandwidths ofthe third and fourth microphones may be equal to each other.

Alternatively, the frequency responses of the third and fourthmicrophones may have different frequency bandwidths. For example, asshown in FIG. 40B, the frequency response 4030 of the fourth microphonehas a lower half-power point f₂, an upper half-power point f₇ (which isgreater than f₄), and a center frequency f₆. The frequency bandwidth ofthe frequency response 4030 of the fourth microphone may be equal to adifference between f₇ and f₂, which may be greater than that of thefrequency response 4010 of the third microphone. In this way, fewermicrophones may be needed in the microphones 3910 a to generate aplurality of sub-band sound signals to cover the frequency band of theoriginal sound (i.e., the sound S).

In some embodiments, the frequency responses of the third microphone andthe fourth microphone may intersect at a certain frequency point, whichmay cause a certain overlap between the third and fourth frequencyresponses. Ideally, there may be no overlap between the frequencyresponse of the third and fourth microphones. However, in practice,there may be a certain overlap range, which may cause an overlap betweenthe frequency bands of the first and second sub-band sound signals inthe frequency domain, further affecting the quality of the first andsecond sub-band sound signals. For example, the larger the overlaprange, the lower the quality of the first and second sub-band soundsignals may be.

In some embodiments, the certain frequency point at which the frequencyresponses of the third and the fourth microphones intersects may be neara half-power point of the frequency response of the third microphoneand/or a half-power point of the frequency response of the fourthmicrophone. Taking FIG. 40A as an example, the frequency response 4010and the frequency response 4020 intersect at the upper half-power pointf₂ of the frequency response 4010, which is also the lower half-powerpoint of the frequency response 4020. As used herein, a frequency pointmay be considered to be near a half-power point if a power leveldifference between the frequency point and the half-power point is nolarger than a threshold (e.g., 2 Db). In such cases, there may be lessloss or repetition of energies in the frequency responses of the thirdand fourth microphones, which may result in a proper overlap rangebetween the frequency responses of the third and fourth microphones. Insome embodiments, the overlap range may be deemed relatively small whenthe frequency responses intersect at a frequency point with a powerlevel larger than −5 Db and/or smaller than −1 Db. In some embodiments,center frequencies and/or bandwidths of the frequency responses of thethird and fourth microphones may be adjusted to obtain a narrower orproper overlap range between the frequency responses of the third andfourth microphones, so as to avoid an overlap between the frequencybands of the first and second sub-band noise signals.

It should be noted that the examples shown in FIGS. 40A and 40B areintended to be illustrative, and not to limit the scope of the presentdisclosure. For a person having ordinary skill in the art, multiplevariations and modifications may be made under the teachings of thepresent disclosure. However, those variations and modifications do notdepart from the scope of the present disclosure. For example, one ormore parameters (e.g., the frequency bandwidth, an upper half powerpoint, a lower half power point, and/or a center frequency) of afrequency response of the third microphone and/or the fourth microphonemay be variable.

FIG. 41 is a schematic diagram illustrating an exemplary sub-band noisesuppression sub-unit 4100 according to some embodiments of the presentdisclosure. As described in FIG. 39A, the sub-band noise suppressionsub-unit 4100 may be included in the sub-band noise reduction units 3922a. The sub-band noise suppression sub-unit 4100 may be configured toreceive a sub-band noise signal N_(i)(n) from a sub-band noiseestimation sub-unit of a sub-band noise reduction unit 3912 a or 3912 b,and generate a sub-band noise correction signal A_(t)N′_(i)(n) forreducing the sub-band noise signal N_(i)(n). A_(t) may refer to anamplitude attenuation coefficient relating to a noise to be reduce.

As shown in FIG. 41 , the sub-band noise suppression sub-unit 4100 mayinclude a phase modulator 4110 and an amplitude modulator 4120. Thephase modulator 4110 may be configured to receive the sub-band noisesignal N_(i)(n) and generate a phase-modulated signal N′_(i)(n) byinversing the phase of the sub-band noise signal S_(i)(n). For example,as shown in FIG. 42 , the phase-modulated signal N′_(i)(n) may have aninverted phase to the sub-band noise signal N_(i)(n). In someembodiments, a phase displacement (or shift) of the noise may occurduring its transmission from a location at the microphones 3912 a-i to alocation at the corresponding sub-band noise reduction unit 3922 a-i. Insome embodiments, the phase displacement may be neglected. The phasemodulator 4110 may generate the phase-modulated signal N′_(i)(n) bymerely performing a phase inversion on the sub-band noise signalN_(i)(n). A sound may be transmitted in the form of a plane wave in anexternal auditory canal if a frequency of the sound is lower than acutoff frequency of the external auditory canal. When a noise istransmitted in a form of a plane wave along a single direction duringits transmission from a location at the microphones 3912 a-i to alocation at the corresponding sub-band noise reduction unit 3922 a-i, ifthe phase displacement is less than a threshold, the phase displacementmay be neglected in generating the phase-modulated signal N_(i)′(n); ifthe phase displacement is greater than a threshold, a phase compensationmay be performed on the sub-band noise signal N_(i)(n).

Merely by way of example, the phase of the sub-band noise signalS_(i)(n) may have a phase displacement Δφ during its transmission from alocation at the microphones 3912 a-i to a location at the correspondingsub-band noise reduction unit 3922 a-i. The phase displacement Δφ may bedetermined according to Equation (8) as below:

$\begin{matrix}{{{\Delta\varphi} = {\frac{2\pi f_{0}}{c}\Delta d}},} & {{Equation}(8)}\end{matrix}$where f₀ may refer to a center frequency of the sub-band noise signalN_(i)(n), and c may refer to a travelling speed of sound. If the noiseis a near-field signal, Δd may refer to a difference between a distancefrom the sound source to the microphones 3912-i and a distance from thesound source to the corresponding sub-band noise reduction unit 3922 a-i(or a portion thereof). If the noise 210 is a far-field signal, Δd maybe equal to d cos θ, wherein d may refer to a distance between themicrophones 3912-i and the corresponding sub-band noise reduction unit3922 a-i (or a portion thereof), and θ refers to an angle between thesound source and the microphones 3912-i and the corresponding sub-bandnoise reduction unit 3922 a-i (or a portion thereof).

In order to compensate for the phase displacement Δφ, the phasemodulator 4110 may perform a phase inversion as well as a phasecompensation on the sub-band noise signal N_(i)(n) to generate a phasemodulated signal. In some embodiments, the phase modulator 710 mayinclude an all-pass filter. A filter function of the all-pass filter maybe denoted as H(w), wherein w refers to an angular frequency. In anideal situation, an amplitude response |H(w)| of the all-pass filter maybe equal to 1, and a phase response of all-pass filter may be equal tothe phase displacement Δφ. The all-pass filter may delay the sub-bandnoise signal S_(i)(n) by a time delay ΔT to perform the phasecompensation, ΔT may be determined according to Equation (9) as below:

$\begin{matrix}{{\Delta T} = {\frac{\Delta\varphi}{2\pi f_{0}} = {\frac{\Delta d}{c}.}}} & {{Equation}(9)}\end{matrix}$

In such cases, the phase modulator 4110 may perform a phase inversionand a phase compensation on the sub-band noise signal N_(i)(n) togenerate a target modulated signal A_(t)N′_(i)(n).

The amplitude modulator 4120 may be configured to receive thephase-modulated signal N′_(i)(n), and generate the correction signalA_(t)N′_(i)(n) by modulating the amplitude of the phase-modulated signalN′_(i)(n). In some embodiments, an amplitude the noise may attenuateduring its transmission. An amplitude attenuation coefficient A_(t) maybe determined to measure the amplitude attenuation of the noise duringthe transmission. The amplitude attenuation coefficient A_(t) may beassociated with one or more factors including, for example, the materialand/or the structure of an acoustic channel component along which thenoise is transmitted, a location of the microphones 3912 a-i relative toand the corresponding sub-band noise reduction unit 3922 a-i, or thelike, or any combination thereof. In some embodiments, the amplitudeattenuation coefficient A_(t) may be a default setting of a noisereduction system (e.g., the noise reduction system 3800) or previouslydetermined by an actual or simulated experiment. Merely by way ofexample, the amplitude attenuation coefficient A_(t) may be determinedby comparing an amplitude of a sound signal near the microphones 3912a-i (e.g., before it enters an audio broadcast device) and an amplitudeof the sound signal after it is transmitted to a location at thecorresponding sub-band noise reduction unit 3922 a-. In some alternativeembodiments, the amplitude attenuation of the noise may be neglected,for example, if the amplitude attenuation during the transmission of thenoise is smaller a threshold and/or the amplitude attenuationcoefficient A_(t) is substantially equal to 1. In such cases, thephase-modulated signal N′_(i)(n) may be designated as the sub-band noisecorrection signal of the sub-band noise signal N_(i)(n).

The sub-band noise suppression sub-unit 4100 may include a sub-bandsound signal generator (not shown). The sub-band sound signal generatormay generate a sub-band noise correction sound signal Ci (n) accordingto the target modulated signal A_(t)N′_(i)(n) and the correspondingsub-band sound signal S_(i)(n), and transmit it to the combinationdevice 3830. The combination device 3830 may combine a plurality ofsub-band noise correction into one target signal S′(n) according toEquation (10) as below:S′(n)=Σ_(i=1) ^(m) C _(i)(n).  Equation (10)

It should be noted that the examples shown in FIGS. 41 and 42 areintended to be illustrative, and not to limit the scope of the presentdisclosure. For a person having ordinary skill in the art, multiplevariations and modifications may be made under the teachings of thepresent disclosure. However, those variations and modifications do notdepart from the scope of the present disclosure. For example, thesub-band noise suppression sub-unit 4100 may include one or moreadditional components, such as a signal combination unit. Additionallyor alternatively, one or more components in the above-mentioned sub-bandnoise suppression subunit 4100 may be omitted, for example, theamplitude modulator 4120.

FIGS. 43A and 43B are schematic diagrams of exemplary smart glassesaccording to some embodiments of the present disclosure. The smartglasses 4300 may include a supporting structure to be worn on a user'sbody and lenses 4330 (for example, lenses 4330-1 and 4330-2). Thesupporting structure may include a frame 4310 and legs 4320 (including aright leg 4320-1 and a left leg 4320-2). The frame 4310 may include anoise pad 4312. The frame 4310 may be used to support the lens 4330. Thenoise pad 4312 may be provided in the middle of the mirror frame 4310and may be placed on the bridge of a user's nose when wearing the smartglasses 4300. The legs 4320 may be placed on the user's ear when wearingthe smart glasses 4300. In some embodiments, the frame 4310 may beconnected to the legs 4320 through a connection structure 4340 to form apair of glasses with foldable legs 4320. In some embodiments, the frame4310 may be detachably connected to the legs 4320. Exemplary connectionstructure 4340 may include a snap-in structure, a plug-in structure, ahinge structure, or the like, or a combination thereof. In someembodiments, the frame 4310 and the legs 4320 may be integrally formedinto one piece.

The lenses 4330 may be of any suitable type. For example, the lenses4330 may include a plano lens, a diopter lens (e.g., a hyperopia lens, amyopia lens), a sunglasses lens, a 3D lens, or the like. As anotherexample, the lenses 4330 may include a lens having an augmented reality(AR) function and/or a virtual reality (VR) function. In someembodiments, the smart glasses 4300 may receive an instruction (e.g., amode switching instruction among a normal mode, a VR mode, and an ARmode). The lenses 4330 may automatically adjust its light transmittanceand/or haze according to the received instruction and call a miniprojection device (not shown) to achieve a mode switching instructionamong a normal mode, a VR mode, and an AR mode. For example, afterreceiving the instruction to switch to the AR mode, the smart glasses4300 may control the light transmittance of the lenses 4330 to decreaseby an appropriate amount, and project an AR image or video in front ofthe user's line of sight via calling the mini projection device. Asanother example, after receiving the instruction to switch to the VRmode, the smart glasses 4300 may control the haze of the lenses 4330 toincrease by nearly 100%, and project a VR image or video inside thelenses 4330 via calling the mini projection device. In some embodiments,the lenses 4330 may include a spherical surface, an aspherical surface,a toric surface, or the like, or any combination thereof. In someembodiments, the lenses 4330 may be made of plastic materials (e.g.,polyurethane, epoxy plastic, allyl diethylene glycol carbonate plastic),a glass material (e.g., mineral glass, plexiglass), etc.

The legs 4320 (for example, the left 4320-2) may include a front end4322 and a hook-shaped structure that is integrally formed with thefront end 4322 into one piece. The hook-shaped structure may be hookedat the rear end 4324 of the user's ear when the user wears the smartglasses 4300. In some embodiments, in order to save material and improvewearing comfort, a cross-sectional area of the rear end 4324 may besmaller than that of the front end 4322, that is, the rear end 4324 isthinner than the front end 4322. In some embodiments, a stable structure(e.g., a stable structure 4660 shown in FIG. 46A) may be provided at themiddle portion of the legs 4320. The stable structure may be used to fixthe smart glasses 4300 on the user's ear, avoiding the smart glasses4300 from easily slipping off the user's ear.

The supporting structure may be made of any suitable materials. In someembodiments, the frame may be integrally formed, or assembled byplugging, snapping, or the like. In some embodiments, the materials usedto make the frame may include, but not limited to, metal, alloy,plastic, fiber, and other single or composite materials. The metal mayinclude, but not limited to, copper, aluminum, titanium, gold, stainlesssteel, carbon steel, or the like. The alloy may include, but is notlimited to, aluminum alloy, chromium-molybdenum steel, rhenium alloy,magnesium alloy, titanium alloy, magnesium-lithium alloy, nickel alloy,or the like. The plastic may include, but not limited to,acrylonitrile-butadiene-styrene copolymer (Acrylonitrile butadienestyrene, ABS), polystyrene (PS), high impact polystyrene (HIPS),polypropylene (PP), polyethylene terephthalate (PET), polyester (PES),polycarbonate (PC), polyamide (PA), polyvinyl chloride (PVC),polyethylene and blown nylon, or the like. The fiber may include acetatefiber, propionate fiber, carbon. The single or composite materials mayinclude, but not limited to, glass fiber, carbon fiber, boron fiber,graphite fiber, graphene fiber, silicon carbide fiber, aramid fiber andother reinforcing materials; or a composite of other organic and/orinorganic materials, such as glass fiber reinforced unsaturatedpolyester, various types of glass steel with epoxy resin or phenolicresin, etc. In some embodiments, the materials of the frame 4310 and thelegs 4320 may be the same or different. For example, the frame 4310 maybe made of plastic material, and the legs 4320 may be made of a metalmaterial. For another example, the frame 4310 may be made of plasticmaterial, and the legs 4320 may be made of a metal material and aplastic material. In some embodiments, a sheath may be provided on theleg 4320-1 and/or the leg 4320-2. The sheath may be made of softmaterial with a certain elasticity, such as silicone, rubber, etc., soas to provide a better touch for the user.

As shown in FIG. 43B, a vertical distance h1 of a line connecting asymmetrical center point of the frame 4310 to a center point of the endsof the two legs 4320-1 and 4320-2 may be equal to 8 cm-20 cm.Preferably, a range of h1 may be 8.5 cm-19 cm; more preferably, therange of h1 may be 9 cm-18 cm; more preferably, the range of h1 may be9.5 cm-17 cm; more preferably, the range of h1 may be 10 cm-16 cm; morepreferably, the range of h1 may be 10.5 cm-15 cm; more preferably, therange of h1 may be 11 cm-14 cm; more preferably, the range of h1 may be11.5 cm-13 cm. A distance h2 between center points of two connectingstructures connected to the two legs 4320-1 and 4320-2 may range from 7cm to 17 cm. Preferably, the range of h2 may be 7.5 cm-16 cm; morepreferably, the range of h2 may be 8 cm-15 cm; more preferably, therange of h2 may be 8.5 cm-14 cm; more preferably, the range of h2 Therange may be 9 cm-13 cm; more preferably, the range of h2 may be 9.5cm-12 cm; more preferably, the range of h2 may be 10 cm-11 cm.

In some embodiments, the smart glasses 4300 may be provided with aplurality of components which may implement different functions.Exemplary components may include a power source assembly for providingpower, an acoustic driver for generating sound, a microphone fordetecting external sound, a Bluetooth module for connecting to otherdevices, a controller for controlling the operation of other components,or the like, or any combination thereof. In some embodiments, theinterior of the frame 4310, and the leg 110 and/or the leg 120 may beprovided as a hollow structure for accommodating the one or morecomponents. For example, an acoustic output devices (e.g., the acousticoutput device 400, the acoustic output apparatuses 500A/500B, theacoustic output apparatuses 600A/600B, the acoustic output apparatuses700A/700B), a noise reduction system (e.g., the noise reduction system3800, the noise reduction systems 3900A/3900B), a circuit board, abattery slot, etc. may be set in the hollow structure.

The acoustic output device may be used to output sound to a user. Insome embodiments, the acoustic output device may include a plurality ofsets of low-frequency acoustic drivers and a plurality of sets ofhigh-frequency acoustic drivers. One or more sound guiding holes may beconnected to the low-frequency acoustic drivers and the high-frequencyacoustic drivers, respectively. In some embodiments, when a distancebetween the sound guiding holes coupled to the high-frequency acousticdriver is smaller than a distance between the sound guiding holescoupled to the low-frequency acoustic driver, a sound volume to be heardby the user's ear may be increased, so as to reduce the sound leakage ofthe acoustic output apparatus, thereby preventing sounds from beingheard by others near the acoustic output device. In some embodiments,the acoustic output device may include a plurality of sets of acousticdrivers. For example, as shown in FIG. 46A, the sets of acoustic driversmay include an acoustic driver 4640 and an acoustic driver 4650. The leg4600A may be provided with a sound guiding hole 4645 and a sound guidinghole 4655, which are coupled to the acoustic driver 4640 and theacoustic driver 4650, respectively. The acoustic driver 4650 and thesound guiding hole 4655 may be provided at the rear end 4624 of the leg4600A. The sound guiding hole 4645 and the sound guiding hole 4655 maybe regarded as two point sound sources. In some embodiments, a bafflestructure may be provided on the acoustic output apparatus, so that theat least two sound guiding holes may be distributed on both sides of thebaffle, respectively. In general, a baffle structure may be providedbetween the two point sound sources, which may significantly increasethe sound volume in the near-field without significantly increasing thesound leakage volume in the far-field leakage, thereby improving theuser's listening experience. When the user wears the smart glasses withlegs 4600A, the sound guiding hole 4645 may be located on the front sideof the ear, and the sound guiding hole 4655 may be located on the backside of the ear. At this time, the auricle may serve as a bafflestructure between the sound guiding hole 4645 and the sound guiding hole4655. The auricle may increase a distance between the sound guiding hole4645 and the sound guiding hole 4655. When the smart glasses 4300 areplaying sound, the baffle structure may significantly increase the soundvolume in the near-field, which may improve the user's listeningexperience. More descriptions regarding the acoustic output apparatusmay be found elsewhere in the present disclosure. See, e.g., FIGS. 1-37and relevant descriptions thereof.

The noise reduction system may include a microphone array, a noisereduction device, a combination device, and the like. The microphones inthe microphone array may be used to generate sub-band sound signals. Thenoise reduction device may be configured to generate a target modulatedsignal having an inverted phase to the sub-band noise signal accordingto a sub-band noise signal in the sub-band voice signal, to reduce anoise of the sub-band sound signal and generate a corresponding sub-bandnoise reduction signal. A plurality of sub-band noise reduction signalsmay be transmitted to a combination device to be combined into a targetsignal. More descriptions regarding the noise reduction system may befound elsewhere in the present disclosure. See, e.g., FIGS. 38, 39A, 39Band relevant descriptions thereof. In some embodiments, the microphonearray may be disposed on the leg 4320 and/or the frame 4310. Moredescriptions regarding positions of the microphone array may be foundelsewhere in the present disclosure. See, e.g., FIGS. 44A, 44B, 45A, and45B and relevant descriptions thereof.

In some embodiments, the positions of the noise reduction device and thecombination device in the smart glasses 4300 may be randomly set, whichis not limited herein. For example, the noise reduction device and thecombination device may be integrated together on a circuit board. Asanother example, the noise reduction device and the synthesis device maybe disposed at the leg 4320 and the frame 4310, respectively. In someembodiments, a Bluetooth module may be integrated on the circuit board.A battery slot on the circuit board may be used to install a battery toprovide power for the circuit board. Through the integrated Bluetoothmodule, the smart glasses 4300 may implement functions such as makingand receiving calls, and listening to music.

FIGS. 44A and 44B are schematic diagrams of exemplary legs according tosome embodiments of the present disclosure. As shown in FIGS. 44A and44B, the legs 4320 may be a hollow structure. A microphone array 4410(for example, a microphone array 3810 in the microphone noise reductionsystem 3800), a circuit board 4420, a battery slot 4430, an acousticoutput device 4440, and the like, may be disposed in the hollowstructure. In some embodiments, the hollow structure may further includea noise reduction device and a combination device (not shown). The leg4320 may further be provided with a sound inlet 4415 (or a sound inputhole) that cooperates with the microphone array 4410, and a sound outlet4445 (or sound guiding hole) that cooperates with the acoustic outputdevice 4440 (as shown in FIG. 44B). It should be noted that thepositions of components such as the microphone array 4410, the circuitboard 4420, the battery slot 4430, and the acoustic driver 4440 may beadjusted in the hollow structure according to needs during the setting,and need not be the same as those in FIG. 44A. For example, the batteryslot 4430 and the circuit board 4420 may be swapped. As another example,the microphone array 4410 may be disposed at the rear end 4424. In someembodiments, the microphone array may also be disposed in the frame 4310(such as the noise pad 4312).

FIGS. 45A and 45B are schematic diagrams of exemplary smart glassesaccording to some embodiments of the present disclosure. As shown inFIGS. 45A and 45B, the microphone array 4510 may be disposed at nose pad4312. The nose pad 4312 may also be provided with the sound inlet hole4515 that cooperates with the microphone array 4510.

In some embodiments, when a user wears the smart glasses 4300, adistance D between a center point of the microphone array 4410 or 4510and a center point of the user's mouth (i.e., the main sound source) mayrange from 2 cm to 20 cm. Preferably, the range of D may be 2.5 cm-18cm; more preferably, the range of D may be 3 cm-16 cm; more preferably,the range of D may be 3.5 cm-14 cm; more preferably, the range of D Therange may be 4 cm-12 cm; more preferably, the range of D may be 4.5cm-10 cm; more preferably, the range of D may be 5 cm-8 cm; morepreferably, the range of D may be 5.5 cm-7.5 cm; more preferably, therange of D may be 6 cm-7 cm.

In some embodiments, the microphone array may include at least one pairof low-frequency microphones and at least one pair of high-frequencymicrophones. The microphones of each pair of microphones may have thesame configuration. The microphones of each pair of microphones maycorrespond to a sub-band sound signal having the same frequency band. Adistance between each pair of low-frequency microphones is equal to adistance between each pair of high-frequency microphones. Forillustration, a microphone closer to the main sound source (e.g., auser's mouth) in each pair of microphones may be referred to as a firstmicrophone, and a microphone farther away from the main sound source inthe pair of microphones may be referred to as a second microphone. FIG.46A is a schematic diagram of an exemplary leg according to someembodiments of the present application. As shown in FIG. 46A, in thehollow structure of the leg 4600A, two sets of microphones correspondingto each other may be provided (that is, the microphone array may includetwo sets of microphones corresponding to each other), for example, afirst microphone set 4612 and a second microphone set 4614. Each of thefirst microphone set 4612 and the second microphone set 4614 may includea plurality of microphones configured to a plurality of sub-band soundsignals having different frequency bands. One first microphone in thefirst microphone set 4612 may match with one second microphone in thesecond microphone set 4614. Each microphone in the first microphone set4612 and/or the second microphone set 4614 may decompose a sound signalinto the sub-band sound signals. For example, after the sound signal isprocessed by the corresponding first microphone and the secondmicrophone, the sub-band sound signals having the same frequency bandmay be obtained.

A distance between the first microphone set 4612 and the main soundsource (e.g., the user's mouth) may be shorter than a distance betweenthe second microphone set 4614 and the main sound source. In someembodiments, the first microphone set 4612 and the second microphone set4614 may be distributed in the leg 4600A in a specific manner so thatthe main sound source is located in a direction from the secondmicrophone set 4614 to the first microphone set 4612.

In some embodiments, when the user wears the smart glasses 4300 equippedwith leg 4600A, since the user's mouth (that is, the main sound source)is closer to a first microphone 4612-i and a corresponding secondmicrophone 4614-i than other sound sources (e.g., noise sources) in theenvironment, the mouth may be considered as a near-field sound source ofthe first microphone 4612-i and second microphone 4614-i. A volume ofthe sound outputted from the near-field sound source and received by thefirst microphone 4612-i and second microphone 4614-i may be associatedwith the distance between the near-field sound source and the firstmicrophone 4612-i or the second microphone 4614-i. Since the firstmicrophone 4612-i is closer to the main sound source than the secondmicrophone 4612-i, the first microphone 4612-i may detect a sound andgenerate a sub-band sound signal V_(J1) with a larger sound volume, andthe second microphone 4612-i may detect the sound and generate asub-band sound signal V_(J2) with a smaller sound volume.

In some embodiments, since a noise source in the environment is far awayfrom the first microphone 4612-i and the second microphone 4614-i, thenoise source may be considered as a far-field sound source of the firstmicrophone 4612-i and the second microphone 4614-i. The first microphone4612-i may detect a noise and generate a sub-band noise signal V_(r1),and the second microphone 4614-i may detect the noise and generate asub-band noise signal V_(r2). The sound volume of sub-band noise signalV_(r1) may approximate to the sound volume of sub-band noise signal ofV_(r2), that is, V_(Y1)≈V_(Y2).

Thus, a combination signal V₁ generated by the first microphone 4612-imay be determined according to Equation (11), as below:V ₁ =V _(J1) +V _(Y1),  (11)

And a combination signal V₂ generate by the second microphone 4614-i maybe determined according to Equation (12), as below:V ₂ =V _(J2) +V _(Y2),  (12)

In order to eliminate or reduce the sub-band noise signal(s) in thecombined signal(s), a differential signal V may be determined bydifferentiating combination signal V₁ and the combination signal V₂according to Equation (13), as below:V=V ₁ −V ₂=(V _(J1) −V _(J2))+(V _(Y1) −V _(Y2))≈V _(J1) −V _(J2),  (13)

Further, the sub-band sound signals V_(J1) and V_(J2), which is actuallyobtained from the main sound source by the first microphone 4612-i orthe second microphone 4614-i, may be determined based on the determineddifferential signal V and the distances of the first microphone 4612-iand the second microphone 4614-i with respect to the main sound source.In some embodiments, the differential signal V of each sub-band soundsignal may be amplified, and then inputted to a combination device (notshown) for further processing, so as to generate a target signal. Thetarget signal may be propagated to the user via the acoustic driver 4640and/or the acoustic driver 4650.

In some embodiments, the first microphone group 4612 and/or the secondmicrophone group 4614 may be disposed on the leg 4600A and/or the frame4670 (as shown in FIGS. 46A and 46B). To ensure the quality of thesub-band sound signals V_(J1) and V_(J2), the differential signal Vdetermined according to the Equation (13) may be made as large aspossible, that is, V_(J1)>>V_(J2). In some embodiments, a position ofthe first microphone set 4612 may be as close as possible to the mainsound source (e.g., the user's mouth), and a position of the secondmicrophone set 4614 may be as far away as possible from the main soundsource. In some embodiments, a baffle structure may be provided betweenthe two microphone sets. For example, the first microphone set 4612 maybe disposed at the front end 4622 of the leg 4600A, and the secondmicrophone set 4614 may be disposed at the rear end of the leg 4624.When a user wears a smart glass (e.g., the smart glasses 4300) with theleg 4600A, the auricle may function as a baffle structure between thefirst microphone set 4612 and the second microphone set 4614, whichenlarges a distance between the first microphone set 4612 and the secondmicrophone set 4614. In some embodiments, the distance from the mainsound source to the first microphone set 4612 may be the equal to thedistance from the main sound source to the microphone array 4410 or themicrophone array 4510. In some embodiments, a distanced between thefirst microphone set 4612 and the second microphone set 4614 (as shownin FIG. 46A or 46B) may be not less than 0.2 cm. Preferably, d may benot less than 0.4 cm; more preferably, d may be not less than 0.6 cm;more preferably, d may be not less than 0.8 cm; more preferably, d maybe not less than 1 cm; more preferably, d may be not less than Less than2 cm; more preferably, d may be not less than 3 cm; more preferably, dmay be not less than 4 cm; more preferably, d may be not less than 5 cm;more preferably, d may be not less than 6 cm; more preferably Ground, dmay be not less than 7 cm; more preferably, d may be not less than 8 cm;more preferably, d may be not less than 9 cm; more preferably, d may benot less than 10 cm; more preferably, d may be not less than 11 cm; morepreferably, d may be not less than 12 cm; more preferably, d may be notless than 13 cm; more preferably, d may be not less than 14 cm; morepreferably, d may be not less than 15 cm; more preferably, d may be notless than 17 cm; more preferably, d may be not less than 19 cm; morepreferably, d may be not less than 20 cm.

In some embodiments, a distance between each pair of microphones in themicrophone array may be different. A distance between the low-frequencymicrophones may be greater than a distance between the high-frequencymicrophones. FIG. 47 is a schematic diagram of exemplary smart glassesaccording to some embodiments of the present disclosure. As shown inFIG. 47 , the smart glasses 4700 may include at least one pair oflow-frequency microphones (e.g., a low-frequency microphone 4710 and alow-frequency microphone 4720) and at least one pair of high-frequencymicrophones (e.g., a high-frequency microphone 4730 and a high-frequencymicrophone 4740). A distance between the low-frequency microphones 4710and 4720 may be greater than a distance between the high-frequencymicrophones 4730 and 4740. By setting different distances formicrophones having different frequencies, a sound receiving effect ofthe smart glasses 4700 can be improved. The reason is that, when aposition of a far-field sound source is constant, a low-frequency soundoutputted by the far-field sound source may have a low-frequency and along period, and a high-frequency sound outputted by the far-field soundsource may have a high-frequency and a short period. Properly increasingthe distance between the low-frequency microphones 4710 and 4720 maysignificantly improve a near-field sound receiving effect withoutsignificantly increasing a far-field low-frequency noise, since a phaseshift caused by the increasing distance between the low-frequencymicrophones 4710 and 4720 only occurred at a small portion of theperiod. Properly increasing the distance between the high-frequencymicrophones 4730 and 4740 may gradually reduce a phase differencebetween the far-field high-frequency noise generated by thehigh-frequency microphones 4730 and 4740, which may well eliminate thehigh-frequency noise. Therefore, by setting the distance between thehigh-frequency microphones to be smaller than the distance between thelow-frequency microphones, and then using a differential operation for anoise reduction, the far-field noise (including a far-fieldlow-frequency noise and a far-field high-frequency noise) may beeliminated or approximately eliminated. It should be noted that thepositions of the low-frequency microphone 4710, the low-frequencymicrophone 4720, the high-frequency microphone 4730, and thehigh-frequency microphone 4740 shown in FIG. 47 are merely forillustration, and each microphone of them may be disposed at anothersuitable position of the smart glasses 4700. For example, thelow-frequency microphone 4710 and the low-frequency microphone 4720 maybe disposed on a frame, and the high-frequency microphone 4730 and thehigh-frequency microphone 4740 may be disposed on a leg. As anotherexample, the low-frequency microphone 4710 may be disposed on the frame,and the low-frequency microphone 4720, the high-frequency microphone4730, and the high-frequency microphone 4740 may be disposed on the leg.In some embodiments, the distance d_(l) between the low-frequencymicrophones 4710 and 4720 may be 0.8 cm-20 cm; preferably, the rdistance d_(l) may be 1 cm-18 cm; more preferably, the distance d_(l)may be 1.2 cm-16 cm; more preferably, the distance d_(l) may be 1.4cm-14 cm; more preferably, the distance d_(l) may be 1.6 cm-12 cm; morepreferably, the distance d_(l) may be 1.8 cm-10 cm; more preferably, thedistance d_(l) may be 2 cm-8 cm; more preferably, the distance d_(l) maybe 2.2 cm-6 cm; more preferably, the distance d_(l) may be 2.4 cm-4 cm;more preferably, the distance d_(l) may be 2.6 cm-3.8 cm; morepreferably, the distance d_(l) may be 2.8 cm-3.6 cm; more preferably,the distance d_(l) may be 3 cm. In some embodiments, the distance d_(h)between the high-frequency microphones 4730 and 4740 may range from 1 mmto 12 mm; preferably, the distance d_(h) may be 1.2 mm to 11 mm; morepreferably, the distance d_(h) may be 1.2 mm-10 mm; more preferably, thedistance d_(h) may be 1.4 mm-9 mm; more preferably, the distance d_(h)may be 1.6 mm-8 mm; more preferably, the distance d_(h) may be 1.8mm-7.5 mm; more preferably, the distance d_(h) may be 2 mm-7 mm; morepreferably, the distance d_(h) may be 2.5 mm-6.5 mm; more preferably,the distance d_(h) may be 3 mm-6 mm; more Preferably, the distance d_(h)may be 3.5 mm-5.5 mm; more preferably, the distance d_(h) may be 4mm-5.3 mm; more preferably, distance d_(h) may be 5 mm. In someembodiments, a frequency band of the human voice may mainly be within alow and medium frequency bands. The low-frequency microphone 4710 may beset closer to the main sound source than the high frequency microphone4730, so as to receive a stronger signal that is within the low andmedium frequency band. The distance between the low-frequencymicrophones 4710 and the main sound source may be the same as thedistance between the microphone array 4410 and the main sound source,and details are not repeated herein.

It should be noted that the above descriptions of smart glasses (forexample, smart glasses 4300, smart glasses 4600B, and smart glasses4700) and/or legs (for example, leg 4320, leg 4600A) are merely providedfor the purposes of illustration, and not intended to limit the scope ofthe present disclosure. For persons having ordinary skills in the art,various modifications and changes in the forms and details of the abovesmart glasses may occur without departing from the principles of thepresent disclosure. However, these changes and modifications do notdepart from the scope of the present application. For example, the lens4330 may be omitted from the smart glasses 4300. As another example, thesmart glasses 4300 may include only one lens. The stable structure 4660may be integrally formed with the leg 4600A, or may be detachablydisposed on the leg 4600A.

In some embodiments, a noise reduction system in smart glasses (forexample, smart glasses 4300, smart glasses 4600B, smart glasses 4700)may detect a sound of a user wearing the smart glasses through a soundinlet hole, and generate a target signal (an electrical signal) byprocessing the detected sound, and transmit the target signal to anobject or device that communicates with the smart glasses. In someembodiments, an acoustic output device in the smart glasses may receivethe target signal transmitted by the object or device that communicateswith the smart glasses, convert the target signal into a target sound(an audio signal), and output the target sound to a user wearing thesmart glasses through a sound guiding hole.

FIG. 48 is a schematic diagram of an exemplary acoustic output apparatusaccording to some embodiments of the present disclosure. In someembodiments, the acoustic output apparatus 4800 may have a similarconfiguration as that of the smart glasses 4300. As shown in FIG. 48 ,the acoustic output apparatus 4800 may include a supporting structurethat enables the acoustic output apparatus 4800 to be located off a userear (e.g., worn by a user over the head), and lenses 4840. Thesupporting structure may include a frame 4830, legs 4810 and 4820, anose pad 4850, or the like. At least a part of the abovementionedcomponents of the acoustic output apparatus 4800 may be similar to orthe same as that of smart glasses 4300, and detailed descriptionsthereof are not repeated herein.

The acoustic output apparatus 4800 may be provided with a plurality ofhollow structures. In some embodiments, shapes, sizes, and counts of theone or more hollow structures on the acoustic output apparatus 4800 mayvary according to actual needs. For example, the shapes of the hollowstructures may include, but not limited to, a square shape, a rectangleshape, a triangle shape, a polygon shape, a circle shape, an ellipseshape, an irregular shape, or the like. As shown in FIG. 48 , the leg4810 may be a hollow structure provided with a sound inlet hole 4811 andmay contain an audio sensor 4812, a controller 4813, a target soundgeneration module 4814, an acoustic driver 4815, one or more soundguiding holes 4816, a scene information generating module 4817, or thelike. The leg 4820 may include one or more components in the leg 4810.As another example, the frame 4850 may be a hollow structure providedwith a sound inlet hole 4811, and housing one or more components in theleg 4810. As another example, the leg 4820 may be a hollow structurecontaining a power button 4821, a sound adjustment button 4822, aplayback control button 4823, a Bluetooth button 4824, a power interface4825, or the like. As yet another example, a noise reduction system(e.g., the noise reduction system 3800, the noise reduction systems3900A/3900B), etc., may be set in the acoustic output apparatus 4800.

The sound inlet hole 4811 may be used to transmit external soundsemitted from a sound source (e.g., a user wearing the acoustic outputapparatus 4800, the acoustic output apparatus 4800, and/or ambientenvironment) to the audio sensor 4812 in the acoustic output apparatus4800. The sound inlet hole 4811 may be provided at a positionfacilitating the acquisition of the user's voice on the glasses 4800,for example, a position near the user's mouth on the leg 4810 and/or4820, a position near the user's mouth under the frame 4830, a positionon the nose pad 4850, or any combination thereof. In some embodiments,the user may interact with the acoustic output apparatus 4800 byspeaking one or more words. The voice of the user may be acquired by theacoustic output apparatus 4800 via the sound inlet hole 4811. It shouldbe noted that the sound inlet hole 4811 can be optional. For example,when there is no need to acquire external sounds emitted from the soundsource(s) around the acoustic output apparatus 4800, there may be nosound inlet holes 4811.

The audio sensor 4812 may be configured to detect a sound via the soundinlet hole 4811, and generate a sound signal in response to the detectedsound. The audio sensor 4812 may include a plurality of microphones or amicrophone array as described elsewhere in the present disclosure, forexample, the microphone array 3910 a or the microphones 3912 a. Asdescribed in connection with FIG. 39A, the audio sensor 4812 maygenerate a plurality of sub-band sound signals according to thefrequency responses of the microphones in the audio sensor 4812. Theaudio sensor 4812 may be electrically coupled to the controller 4812.The sound signal may be transmitted to the controller 4813.

The target sound generation module 4814 may be configured to simulate atarget sound that seems to originate from a virtual object in a virtualreality (VR) scene or an augmented reality (AR) scene. The target soundgeneration module 4814 may generate a first spatial sound signal and asecond spatial sound signal for simulating the target sound. A spatialsound refers to a sound produced by a stereo speaker, a surround-soundspeaker, a speaker-array, or a headphone that indicates binaural spatialcues that permits a listener to locate the sound source of the spatialsound in a three-dimensional (3D) space. Generally, the spatial cues maybe created primarily based on an intensity difference, a phasedifference between the sound at two ears of the listener, a spectralchange of the sound resulting from shapes of a pinnae or an outer ear ofthe listener, the head and torso of the listener, or the like.

The controller 4813 may process data and/or signals obtained from one ormore components (e.g., the audio sensor 4812, the target soundgeneration module 4814) of the acoustic output apparatus 4800. In someembodiments, the controller 4813 may be configured to generate a firstsound signal corresponding to a first frequency range (or referred to asa low frequency range) and a second sound signal corresponding to asecond frequency range (or referred to as a high frequency range). Forexample, the controller 4813 may generate the first sound signal and thesecond sound signal based on the first spatial sound. The controller4813 may generate the first sound signal and the second sound signalbased on the second spatial sound.

The second frequency range may include frequencies higher than the firstfrequency range. For example, the first frequency range may be in arange of 100 Hz-1000 Hz, and the second frequency range may be in arange of 1000 Hz-10000 Hz. More descriptions regarding the first andsecond frequency ranges may be found else wherein in the presentdisclosure. See, e.g., FIG. 4 and relevant descriptions thereof. In someembodiments, the controller 4813 may include one or more components(e.g., the frequency divider 415, the signal processor 420 (or 430)) ofthe electronic frequency division module 410 as described in connectionwith FIG. 4 . For example, the first and second sound signals may begenerated by the frequency divider 415 via decomposing the sound signal.As another example, the first and second sound signals may further beprocessed (e.g., the intensity thereof being adjusted) by the signalprocessor 420. The controller 4813 may be electrically coupled to thetarget sound generation module 4814. The first and second sound signalsmay be transmitted to the controller 4813.

The acoustic driver 4815 may include at least one low-frequency acousticdriver and at least one high-frequency acoustic driver. The at least onelow-frequency acoustic driver may be configured to generate the firstspatial sound based on the first spatial sound signal. The at least onehigh-frequency acoustic driver may be configured to generate a secondspatial sound based on the second spatial sound signal. The at least onelow-frequency acoustic driver may have a similar or same configurationas that of the low-frequency acoustic driver 440 as described inconnection with FIG. 4 . The at least one high-frequency acoustic drivermay have a similar or the same configuration as that of thehigh-frequency acoustic driver 450 as described in connection with FIG.4 . In some embodiments, the at least one low-frequency acoustic drivermay include two first transducers, and the at least one high-frequencyacoustic driver may include two second transducers. The firsttransducers and the second transducers may have different frequencyresponse characteristics. For example, the first transducers may convertthe first spatial sound signals into a first right spatial sound and afirst left spatial sound, respectively. The first right spatial soundmay be outputted from one or more first sound guiding holes located atthe right leg of the acoustic output apparatus 4800, and the first leftspatial sound may be outputted from one or more first sound guidingholes located at the left leg of the acoustic output apparatus 4800. Forexample, the second transducer may convert the second spatial soundsignals into a second right spatial sound and a second left spatialsound, respectively. The second right spatial sound may be outputtedfrom one or more first sound guiding holes located at the right leg ofthe acoustic output apparatus 4800, and the second left spatial soundmay be outputted from one or more first sound guiding holes located atthe left leg of the acoustic output apparatus 4800.

In some embodiments, the supporting structure may be a housing. The atleast one low-frequency acoustic driver may be enclosed by the housing,forming a first front chamber and a first rear chamber corresponding tothe at least one low-frequency acoustic driver. The first front chambermay be acoustically coupled to one of the at least two first soundguiding holes, and the first rear chamber may be acoustically coupled toanother one of the at least two first sound guiding holes. The at leastone high-frequency acoustic driver may be enclosed by the housing,forming a second front chamber and a second rear chamber correspondingto the at least one high-frequency acoustic driver. The second frontchamber may be acoustically coupled to one of the at least two secondsound guiding holes, and the second rear chamber may be acousticallycoupled to another one of the at least two second sound guiding holes.

The one or more sound guiding holes 4816 may include a plurality offirst sound guiding holes acoustically coupled to the at least onelow-frequency acoustic driver and a plurality of second sound guidingholes acoustically coupled to the at least one high-frequency acousticdriver, so as to output the first and second spatial sound to the user.In order to reduce the destructive interference of sounds in thenear-field, a first distance between the first sound guiding holes maybe greater than a second distance between the second sound guidingholes. For example, the first distance may be in a range of 20 mm-40 mm,and the second distance may be in a range of 3 mm-7 mm. In someembodiments, as described in connection with FIG. 4 , one of the firstsound guiding holes may be coupled to the low-frequency acoustic drivervia a first acoustic route, and one of the second sound guiding holesmay be coupled to the high-frequency acoustic driver via a secondacoustic route. The first acoustic route and the second acoustic routemay have different frequency selection characteristics.

The first sound guiding holes may be configured to output the firstspatial sound. For example, the first sound guiding holes on the leg4810 may output the first right spatial sound, and the first soundguiding holes on the leg 4820 may output the first left spatial sound.The second sound guiding holes may be configured to output the secondspatial sound. For example, the second sound guiding holes on the leg4810 may output the second right spatial sound, and the second soundguiding holes on the leg 4820 may output the second left spatial sound.When perceived by the ears of the user, the first and second spatialsound may appear to originate from a sound source located at the knownposition in a VR/AR scene. In some embodiments, the two second soundguiding holes may be located closer to a listening position of a user'sear than the two first sound guiding holes. For example, the two secondsound guiding holes may be provided at a rear end of the leg 4810 and/or4820 being far away from the frame 4830, a bending part 4860 of the leg,or the like.

In some embodiments, the acoustic output apparatus 4800 may include afirst set of first sound guiding holes located in a first region of theacoustic output apparatus and a second set of first sound guiding holeslocated in a second region of the acoustic output apparatus. The firstregion and the second region may be different. In some embodiments, theacoustic output apparatus may include a first set of second soundguiding holes located in a third region of the acoustic output apparatusand a second set of second sound guiding holes located in a fourthregion of the acoustic output apparatus. The third region and the fourthregion may be different. In some embodiments, the first region and thesecond region may be located at opposite sides of the user. In someembodiments, the third region and the fourth region may be located atopposite sides of the user. For instance, the first region and the thirdregion may be located relatively close to the left ear of the user(e.g., located on the left leg of the acoustic output apparatus 4800),and the second region and the fourth region may be relatively close tothe right ear of the user (e.g., located on the right leg of theacoustic output apparatus 4800). More details regarding the soundguiding holes may be found elsewhere in the present disclosure, forexample, in FIG. 50 and the description thereof.

The scene information generating module 4817 may be configured toprocess information related to a VR scene or an AR scene. In someembodiments, the data related to a scene may include video data, audiodata, peripheral data, or the like, or any combination thereof. Forexample, the scene information generating module 4817 may generate ascene according to an instruction or a program (e.g., a gaming program)received from the controller 4813. As another example, the sceneinformation generating module 4817 may receive the data related to theinteraction scenario from a sensor (e.g., a visual sensor, a videosensor, an audio sensor) on the acoustic output apparatus 4800. Thescene information generating module 4817 may provide a correspondingVR/AR sense, by displaying the audio data in the data on a display(e.g., the lenses 4840 or a portion thereof) of the acoustic outputapparatus 4800, and providing the audio data simultaneously (e.g., thetarget sound) via the sound guiding holes 4816 to the user to accompanythe audio data. When the user's head moves or rotates, the sceneinformation generating module 4817 may update the video data and theaudio data according to an updated position of the sound source, andoutput the updated video data and the updated audio data to the user. Insome embodiments, the acoustic output apparatus 4800 may receive aninstruction (e.g., a mode switching instruction among a normal mode, aVR mode, and an AR mode) from the controller 4813. Similar to the lenses4330, the lenses 4840 may automatically adjust its light transmittanceand/or haze according to the received instruction, and call a miniprojection device to achieve a mode switching instruction, and detaileddescriptions are not repeated herein.

The power interface 4825 may be provided on a side of the leg 4810and/or the leg 4820 facing the user's face. Exemplary power interfacesmay include a dock charging interface, a DC charging interface, a USBcharging interface, a lightning charging interface, a wireless charginginterface, a magnetic charging interface, or the like, or anycombination thereof.

The one or more button structures may be used to implement interactionsbetween the user and the acoustic output apparatus 4800. The powerbutton 4821 may include a power-on button, a power-off button, a powerhibernation button, or the like, or any combination thereof. The soundadjustment button 4822 may include a sound increase button, a sounddecrease button, or the like, or any combination thereof. The playbackcontrol button 4823 may include a playback button, a pause button, aresume playback button, a call playback button, a call drop button, acall hold button, or the like, or any combination thereof. The Bluetoothbutton 4824 may include a Bluetooth connection button, a Bluetooth offbutton, a selection button, or the like, or any combination thereof. Insome embodiments, the button structures may be provided on the glasses100. For example, the power button may be provided on the leg 4810, theleg 4820, or the frame 4830. In some embodiments, the one or more buttonstructures may be provided in one or more control devices. The acousticoutput apparatus 4800 may be connected to the one or more controldevices via a wired or wireless connection. The control devices maytransmit instructions input by the user to the acoustic output apparatus4800, so as to control the operations of the one or more components inthe acoustic output apparatus 4800.

In some embodiments, the acoustic output apparatus 4800 may also includeone or more indicators to indicate information of one or more componentsin the acoustic output apparatus 4800. For example, the indicators maybe used to indicate a power status, a Bluetooth connection status, aplayback status, or the like, or any combination thereof. In someembodiments, the indicators may indicate related information of thecomponents via different indicating conditions (for example, differentcolors, different time, etc.). Merely by way of example, when a powerindicator is red, it is indicated that the power source assembly may bein a state of low power. When the power indicator is green, indicatingthat the power source assembly may be a state of full power. As anotherexample, a Bluetooth indicator may flash intermittently, indicating thatthe Bluetooth is connecting to another device. The Bluetooth indicatormay be blue, indicating that the Bluetooth may be connectedsuccessfully.

It should be noted that the above descriptions of the acoustic outputapparatus 4800 are provided for the purposes of illustration, and notintended to limit the scope of the present disclosure. For those skilledin the art, various changes and modifications may be made according tothe description of the present disclosure. In some embodiments, theacoustic output apparatus 4800 may include one or more additionalcomponents. Additionally or alternatively, one or more components of thenoise reduction system 3800 described above may be omitted. For example,the acoustic output apparatus 4800 may include one or more cameras tocapture image data from a real scene around the user (for example, ascene in front of the user). As another example, the acoustic outputapparatus 4800 may also include one or more projectors for projecting animage or a video (for example, the image or video that users see throughthe acoustic output apparatus 4800) onto an external display.

FIG. 49 is a block diagram illustrating an exemplary processor forsimulating a target sound coming from a sound source according to someembodiments of the present disclosure. In some embodiments, theprocessor 4900 may be implemented on an acoustic output apparatus (e.g.,the acoustic output apparatus 4800 shown in FIG. 48 ). In someembodiments, at least a part of the modules of the processor 4900 may beimplemented on one or more independent devices. As shown in FIG. 49 ,the processor 4900 may include a position information determining module4910, a target sound generation module 4920, and an electric frequencydivision module 410. The modules may be hardware circuits of all or partof the processor 4900. The modules may also be implemented as anapplication or set of instructions read and executed by the processor4900. Further, the modules may be any combination of the hardwarecircuits and the application/instructions. For example, the modules maybe part of the processor 4900 when the processor 4900 is executing theapplication/set of instructions.

The position information determining module 4910 may determine positioninformation related to a sound source in a VR/AR scene. In someembodiments, the position information determining module 4910 may obtainstatus information of a user. The status information may includeinformation related to, for example, a location of the user, a gestureof the user, a direction that the user faces, an action of the user, aspeech of the user, or the like, or any combination thereof. The statusinformation of the user may be acquired by one or more sensors mountedon the acoustic output apparatus, such as an Inertial Measurement Unit(IMU) sensor, a camera, a microphone, etc. In some embodiments, theposition information determining module 4910 may determine positioninformation of a sound source with respect to the user based on thestatus information. The sound source may be a virtual object presentedin a VR/AR scene. The position information may be the information of aposition of the virtual object in the VR/AR scene with respect to theuser. For instance, the position information may include a virtualdirection of the sound source with respect to the user, a virtuallocation of the sound source with respect to the user, a virtualdistance between the sound source and the user, or the like, or anycombination thereof.

The target sound generation module 4920 may generate at least two soundsignals for simulating a target sound. The target sound may be a spatialsound that allows the user to identify the position information of thesound source in the VR/AR scene. In some embodiments, there may be adifference between the at least two sound signals that enable the userto hear the spatial sound and identify the position information of thesound source. For example, the difference may include at least one of aphase difference, an amplitude difference, or a frequency difference.

The electronic frequency division module 410 may generate, for each ofthe at least two sound signals, a first sound signal corresponding to afirst frequency range and a second sound signal corresponding to asecond frequency range. The first frequency range and the secondfrequency range may or may not include overlapping frequency ranges. Thesecond frequency range may include frequencies higher than the firstfrequency range. As described in other parts of the present disclosure,in some embodiments, the phases of two first sounds corresponding to thefirst sound signal which are outputted to the user through differentacoustic routes may be different (e.g., opposite). Similarly, the phasesof two second sounds corresponding to the second sound signal which areoutputted to the user through different acoustic routes may be different(e.g., opposite). As a result, the target sound outputted by theacoustic output apparatus may be less likely to be heard by other peoplenear the acoustic output apparatus.

It should be noted that the above description is merely provided for thepurposes of illustration, and not intended to limit the scope of thepresent disclosure. For persons having ordinary skills in the art,multiple variations or modifications may be made under the teachings ofthe present disclosure. However, those variations and modifications donot depart from the scope of the present disclosure. In someembodiments, any module mentioned above may be divided into two or moreunits. For example, the position information determining module 4910 mayinclude an obtaining unit configured to obtain status information of auser and a position information determining unit configured to determineposition information of a sound source based on the status informationof the user.

FIG. 50 is a flowchart of an exemplary process for simulating the targetsound coming from a sound source according to some embodiments of thepresent disclosure. In some embodiments, process 5000 may be implementedby at least a part of the modules shown in FIG. 49 .

In 5002, the position information determining module 4910 may obtainstatus information of a user. As used herein, the term “statusinformation” refers to information related to a location of the user, agesture of the user, a direction that the user faces, an action of theuser (e.g., turning his/her head to a certain direction), a speech ofthe user, or the like, or any combination thereof. In some embodiments,the status information may be detected by one or more sensors mounted onthe acoustic output apparatus, such as an Inertial Measurement Unit(IMU) sensor, a camera, a microphone, etc. For example, the IMU sensormay include but not limited to an acceleration sensor, a gyroscope, ageomagnetic sensor, or the like, or any combination thereof. In someembodiments, the user may interact with the acoustic output apparatus byspeaking a voice command, such as “Power off”, “Start game X”, “Quitgame X”. The microphone may receive the speech of the user and theacoustic output apparatus may identify the voice command. In someembodiments, an interactive menu may be presented by a display of theacoustic output apparatus (e.g., glasses of a smart helmet) for the userto give an instruction to the acoustic output apparatus.

In 5004, the position information determining module 4910 may determineposition information of a sound source with respect to the user based onthe status information. In some embodiments, the sound source may be avirtual object presented in a VR/AR scene. For instance, the VR/AR scenemay be presented to the user via a display (e.g., lenses 4840 or aportion thereof). The position information may be the information of aposition of the virtual object in the VR/AR scene with respect to theuser. In some embodiments, the position information of the virtualobject in the VR/AR scene may be determined based on the statusinformation of the user and information related to the VR/AR scene. Forinstance, the position information may include a virtual direction ofthe sound source with respect to the user, a virtual location of thesound source with respect to the user, a virtual distance between thesound source and the user, or the like, or any combination thereof. Forexample, when the acoustic output apparatus presents a VR scene to theuser and the sound source is a virtual bird, the position informationdetermining module 4920 may determine a virtual position of the virtualbird in the VR scene based on the status information of the user. Merelyby way of example, when the user faces towards North, the virtual birdmay be on the left of the user in the VR scene. When the statusinformation indicates that the user turns his/her head towards the West,the virtual bird may be located in front of the user. The positioninformation may be used for generating a spatial sound (e.g., the chirpof the virtual bird).

In 5006, the target sound generation module 4920 may generate, based onthe position information, at least two sound signals for simulating atarget sound coming from the sound source. As used herein, the targetsound may be a spatial sound that allows the user to identify theposition information of the sound source. For example, the target soundgeneration module 4920 may generate a first spatial sound signal and asecond spatial sound signal for simulating the target sound. In someembodiments, there may be a difference between the at least two soundsignals that enables the user to hear the spatial sound and identify theposition information of the sound source. For example, the differencemay include at least one of a phase difference, an amplitude difference,or a frequency difference. The at least two sound signals may betransmitted to one or more acoustic drivers for generating at least twosounds. In some embodiments, the at least two sounds may be heard by theuser via different acoustic routes. The at least two sounds may beoutputted to the user by different sound guiding holes (e.g., the soundguiding holes 4816 located in different locations of the acoustic outputapparatus 4800).

In some embodiments, the target sound generation module 4920 may apply aspatial sound reproduction algorithm to generate a first spatial soundsignal and a second spatial sound signal, respectively. Exemplaryspatial sound reproduction algorithm may include head-related transferfunctions (HRTFs), a dummy head recording algorithm, a cross-powerspectrum phase (CSP) analysis algorithm, or the like, or any combinationthereof. For illustration purposes, the HRTFs for two ears of thelistener may be used to synthesize the spatial sound that seems to comefrom a particular direction or location in a 3D space. Merely by way ofexample, the target sound generation module 4920 may generate the firstspatial sound signal and the second spatial sound signal in real time.The target sound generation module 4920 may be electrically coupled toan electronic frequency division module 410. The first and secondspatial sound signals may be transmitted to the electronic frequencydivision module 410.

In 5008, for each of the at least two sound signals, the electronicfrequency division module 410 may generate a first sound signal and asecond sound signal. The frequency of a first sound corresponding to thefirst sound signal may be within the first frequency range. Thefrequency of a second sound corresponding to the second sound signal maybe within the second frequency range. In some embodiments, the firstfrequency range may include at least one frequency that is lower than650 Hz. In some embodiments, the second frequency range may include atleast one frequency that is higher than 1000 Hz. In some embodiments,the first frequency range may overlap with the second frequency range.For example, the first frequency range may be 20-900 Hz and the secondfrequency range may be 700-20000 Hz. In some embodiments, the firstfrequency range does not overlap with the second frequency range. Forexample, the first frequency range may be 0-650 Hz (excluding 650 Hz)and the second frequency range may be 650-20000 Hz (including 650 Hz).

In some embodiments, the acoustic output apparatus may include a firstset of first sound guiding holes located in a first region of theacoustic output apparatus and a second set of first sound guiding holeslocated in a second region of the acoustic output apparatus. The firstregion and the second region may be different. In some embodiments, theacoustic output apparatus may include a first set of second soundguiding holes located in a third region of the acoustic output apparatusand a second set of second sound guiding holes located in a fourthregion of the acoustic output apparatus. The third region and the fourthregion may be different. For instance, the first region and the thirdregion may be relatively close to the left ear of the user (e.g.,located on the left leg of the acoustic output apparatus 4800), and thesecond region and the fourth region may be relatively close to the rightear of the user (e.g., located on the right leg of the acoustic outputapparatus 4800).

The first set of first sound guiding holes may include at least twofirst sound guiding holes configured to output the first soundcorresponding to a first spatial sound signal. The second set of firstsound guiding holes may include at least two first sound guiding holesconfigured to output the first sound corresponding to a second spatialsound signal. The first set of second sound guiding holes may include atleast two second sound guiding holes configured to output the secondsound corresponding to a first spatial sound signal. The second set ofsecond sound guiding holes may include at least two second sound guidingholes configured to output the second sound corresponding to a secondspatial sound signal.

In some embodiments, there may be a phase difference between the firstsounds outputted by two first sound guiding holes of the first set offirst sound guiding holes. For example, the phases of the first soundsoutputted by two first sound guiding holes of the first set of firstsound guiding holes may be opposite, which may help preventing theleakage of the first sounds. In some embodiments, similarly, there maybe a phase difference between first sounds outputted by two first soundguiding holes of the second set of first sound guiding holes. In someembodiments, similarly, there may be a phase difference between secondsounds outputted by two second sound guiding holes of the first set ofsecond sound guiding holes. In some embodiments, similarly, there may bea phase difference between the second sounds outputted by two secondsound guiding holes of the second set of second sound guiding holes. Asa result, the target sound simulated based on the first spatial soundsignal and the second spatial sound signal may be less likely to beheard by other people near the acoustic output apparatus.

In some embodiments, there may be a first difference between the firstsound (corresponding to the first spatial sound signal) outputted by thefirst set of first sound guiding holes and the first sound(corresponding to the second spatial sound signal) outputted by thesecond set of first sound guiding holes. In some embodiments, there maybe second difference between the second sound (corresponding to thefirst spatial sound signal) outputted by the first set of second soundguiding holes and the second sound (corresponding to the first spatialsound signal) outputted by the second set of second sound guiding holes.The first difference and the second difference may facilitate the userto identify position information of the sound source of the target sound(i.e., a spatial sound) in the VR/AR scene. For instance, the firstdifference may include at least one of a phase difference, an amplitudedifference, or a frequency difference. The second difference may includeat least one of a phase difference, an amplitude difference, or afrequency difference.

Having thus described the basic concepts, it may be rather apparent tothose skilled in the art after reading this detailed disclosure that theforegoing detailed disclosure is intended to be presented by way ofexample only and is not limiting. Various alterations, improvements, andmodifications may occur and are intended to those skilled in the art,though not expressly stated herein. These alterations, improvements, andmodifications are intended to be suggested by this disclosure, and arewithin the spirit and scope of the exemplary embodiments of thisdisclosure.

We claim:
 1. An acoustic output apparatus, comprising: one or morestatus sensors configured to detect status information of a user; atleast one acoustic driver for outputting sounds based on the statusinformation through at least two sound guiding holes acousticallycoupled to the at least one acoustic driver, wherein: the acousticoutput apparatus is configured to simulate, by outputting the sounds, atleast one target sound coming from a sound source, the target soundbeing a spatial sound that allows the user to identify positioninformation of the sound source, the at least one acoustic driverincludes: at least one low-frequency acoustic driver configured togenerate at least one first sound, a frequency of the at least one firstsound being within a first frequency range; and at least onehigh-frequency acoustic driver configured to generate at least onesecond sound, a frequency of the at least one second sound being withina second frequency range, the at least two sound guiding holes include:at least two first sound guiding holes acoustically coupled to the atleast one low-frequency acoustic driver, the at least two first soundguiding holes being configured to output the at least one first sound;and at least two second sound guiding holes acoustically coupled to theat least one high-frequency acoustic driver, the at least two secondsound guiding holes being configured to output the at least one secondsound, wherein a distance between each of the at least two first soundguiding holes and an ear of the user is greater than a distance betweeneach of the at least two second sound guiding holes and the ear of theuser.
 2. The acoustic output apparatus of claim 1, wherein the secondfrequency range includes at least one frequency that exceeds the firstfrequency range.
 3. The acoustic output apparatus of claim 2, whereinthe first frequency range includes at least one frequency that is lowerthan 650 Hz and the second frequency range includes at least onefrequency that is higher than 1000 Hz.
 4. The acoustic output apparatusof claim 1, wherein the at least one low-frequency acoustic driverincludes a first transducer and the at least one high-frequency acousticdriver includes a second transducer, the first transducer and the secondtransducer having different frequency response characteristics.
 5. Theacoustic output apparatus of claim 4, wherein the first transducerincludes a low-frequency speaker and the second transducer includes ahigh-frequency speaker.
 6. The acoustic output apparatus of claim 1, theacoustic output apparatus further includes: an electronic frequencydivision module configured to divide a sound signal into a first soundsignal corresponding to a sound of the first frequency range and asecond sound signal corresponding to a sound of the second frequencyrange, wherein: the first sound signal is transmitted to the at leastone low-frequency acoustic driver and the second sound signal istransmitted to the at least one high-frequency acoustic driver.
 7. Theacoustic output apparatus of claim 1, wherein there are a first distancebetween the at least two first sound guiding holes and a second distancebetween the at least two second sound guiding holes, the first distancebeing greater than the second distance.
 8. The acoustic output apparatusof claim 1, wherein: the at least two first sound guiding holes includea first set of first sound guiding holes located in a first region ofthe acoustic output apparatus and a second set of first sound guidingholes located in a second region of the acoustic output apparatus, thefirst region of the acoustic output apparatus and the second region ofthe acoustic output apparatus being located at opposite sides of theuser; and the at least two second sound guiding holes include a firstset of second sound guiding holes located in a third region of theacoustic output apparatus and a second set of second sound guiding holeslocated in a fourth region of the acoustic output apparatus, the thirdregion of the acoustic output apparatus and the fourth region of theacoustic output apparatus being located at opposite sides of the user.9. The acoustic output apparatus of claim 8, wherein the at least onetarget sound is simulated based on at least one of: a first differencebetween the at least one first sound outputted by the first set of firstsound guiding holes and the at least one first sound outputted by thesecond set of first sound guiding holes; or a second difference betweenthe at least one second sound outputted by the first set of second soundguiding holes and the at least one second sound outputted by the secondset of second sound guiding holes, the first difference or the seconddifference including at least one of a phase difference, an amplitudedifference, or a frequency difference.
 10. The acoustic output apparatusof claim 1, wherein the at least two first sound guiding holes arecoupled to the at least one low-frequency acoustic driver via a firstacoustic route and the at least two second sound guiding holes arecoupled to the at least one high-frequency acoustic driver via a secondacoustic route, the first acoustic route and the second acoustic routehaving different frequency selection characteristics.
 11. The acousticoutput apparatus of claim 10, wherein the first acoustic route includesan acoustic impedance material, an acoustic impedance of the acousticimpedance material being within a range of 5 MKS Rayleigh to 500 MKSRayleigh.
 12. The acoustic output apparatus of claim 1, wherein theacoustic output apparatus further includes a supporting structureconfigured to: carry the at least one acoustic driver; and enable theacoustic output apparatus to be located off a user ear.
 13. The acousticoutput apparatus of claim 12, wherein the at least two sound guidingholes are located on the supporting structure.
 14. The acoustic outputapparatus of claim 1, wherein the at least one acoustic driver isenclosed in a housing, the housing forming a front chamber of the atleast one acoustic driver and a rear chamber of the at least oneacoustic driver.
 15. The acoustic output apparatus of claim 14, whereinthe front chamber is acoustically coupled to one of at least two soundguiding holes and the rear chamber is acoustically coupled to anotherone of the at least two sound guiding holes.
 16. The acoustic outputapparatus of claim 1, wherein a phase of the sound outputted from one ofthe at least two sound guiding holes is opposite to a phase of the soundoutputted from another one of the at least two sound guiding holes.